BACKGROUND

[0001] The present disclosure relates to methods of additively manufacturing articles via binder jet based printing, in which a liquid bonding agent is selectively deposited to join powder materials.

SUMMARY

[0002] Broadly, the present disclosure relates to methods of making additively manufactured metal-based articles. In one embodiment, a method comprises (a) depositing a first layer of a powder mixture on to a deposition surface, wherein the powder mixture comprises an additive manufacturing feedstock powder and a sintering additive; (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; and (c) repeating steps (a)-(b) to build an additively manufactured article. Due to at least the powder mixtures used to deposit one or more layers of the additively manufactured article on to the deposition surface, the new additively manufactured articles described herein may realize improved densification, lower porosity, lower impurities, and improved homogeneity. Methods of making such additively manufactured articles, powder mixtures and sintering additives associated with making such additively manufactured articles, and physical properties of the additively manufactured articles are described in further detail below.

[0003] In one aspect of the disclosure a method is provided, comprising: (a) depositing a first layer of a powder mixture onto a surface(e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus), wherein the powder mixture comprises an additive manufacturing feedstock powder and a sintering additive ; (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; and (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties of a final additively manufactured article. [0004] In some embodiments, the sintering additive is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

[0005] In some embodiments, the method further comprises heating the additively manufactured article to a first temperature for a sufficient time to remove the binder from the additively manufactured article.

[0006] In some embodiments, the method further comprises heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article (e.g., densifying the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[0007] In some embodiments, the method further comprises densifying the additively manufactured article, wherein the additively manufactured article comprises a first relative density and, wherein the final additively manufactured article comprises a second relative density, wherein the second relative density if greater than the first relative density.

[0008] In some embodiments, the method further comprises at least one of: inspecting the final additively manufactured article, machining the final additively manufactured article, surface treating the final additively manufactured article, surface finishing of the final additively manufactured article, and cleaning the final additively manufactured article.

[0009] In some embodiments, the additive manufacturing feedstock powder comprises at least one of: metal, metal alloys, metal oxides, non-oxides (e.g., borides, carbides, nitrides), or combinations thereof.

[00010] In some embodiments, the sintering additive comprises a single element (e.g. iron). In some embodiments, the sintering additive comprises multiple elements (e.g. iron boride), which multiple elements may be in elemental or compound form. In some embodiments, the sintering additive is at least one of: magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron boride (FeB, Fe ₂ B), silicon boride (S1B3, S1B4), boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaBr,). silicon (Si), magnesium (Mg), yttrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe), and combinations thereof.

[00011] In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 5.0 wt. %.

[00012] In some embodiments, the final additively manufactured article has a sintering additive content of 0.03 wt. % to 5.0 wt. %.

[00013] In some embodiments, the final additively manufactured article has a sintering additive content of 0.05 wt. % to 3.5 wt. %.

[00014] In some embodiments, the final additively manufactured article has a sintering additive content of 0.1 wt. % to 1.0 wt. %.

[00015] In one aspect of the disclosure a method is provided, comprising: (a) heating a metal alloy to form a molten metal alloy; (b) mixing a sintering additive and the molten metal alloy to form a molten metal alloy mixture; (c) forming liquid droplets of the mixed molten metal alloy; (d) cooling the liquid droplets to form a powder comprising the metal alloy and the sintering additive, wherein the powder mixture has a D50 of not greater than 200 microns [00016] In some embodiments, the method further comprises: (a) depositing a first layer of the powder onto a surface (e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder; and (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties of a final additively manufactured article.

[00017] In some embodiments, the sintering additive is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

[00018] In some embodiments, the method further comprises heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article.

[00019] In some embodiments, the method further comprises heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article (e.g., density ing the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[00020] In some embodiments, the surface is one of: a previously bound layer of the binder fluid and the powder or a build substrate of a binder jet 3D printing apparatus.

[00021] In some embodiments, the molten metal alloy is formed by melting metal alloy constituents (e.g., raw material for the alloy).

[00022] In some embodiments, the sintering additive mixed into the molten metal alloy is in powder form.

[00023] In some embodiments, the sintering additive is melted to form molten additives, wherein the molten additives are mixed into the molten metal alloy.

[00024] In some embodiments, the sintering additive and the molten metal alloy are mixed via induction stirring to improve homogenization.

[00025] In some embodiments, the sintering additive and the molten metal alloy are mixed under vacuum to improve degassing.

[00026] In some embodiments, the liquid droplets of the mixed molten metal alloy are formed via atomization (e.g., by forcing the molten metal through an orifice).

[00027] In some embodiments, the metal alloy is a Ti alloy, a Ni alloy, an Al alloy, a Co alloy, a Cu alloy, a Mo alloy, or a Fe alloy. [00028] In some embodiments, the sintering additive comprises a single element (e.g. iron). In some embodiments, the sintering additive comprises multiple elements (e.g. iron boride), which multiple elements may be in elemental or compound form. In some embodiments, the sintering additive is magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron boride (FeB, Fe ₂ B), silicon boride (S1B3, S1B4), boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), yttrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe), or combinations thereof.

[00029] In some embodiments, the molten metal alloy has a sintering additive content of not greater than 5.0 wt. %.

[00030] In some embodiments, the molten metal alloy has a sintering additive content of 0.03 wt. % to 5.0 wt. %.

[00031] In some embodiments, the molten metal alloy has a sintering additive content of 0.1 wt. % to 1.0 wt. %.

[00032] In some embodiments, the cooled powder has a D50 of from 1 micron to 200 microns.

[00033] In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 5.0 wt. %.

[00034] In some embodiments, the final additively manufactured article has a sintering additive content of 0.03 wt. % to 5.0 wt. %.

[00035] In some embodiments, the final additively manufactured article has a sintering additive content of 0.05 wt. % to 3.5 wt. %.

[00036] In some embodiments, the final additively manufactured article has a sintering additive content of 0.1 wt. % to 1.0 wt. %.

[00037] In one aspect of the disclosure a method is provided, comprising: (a) mixing an sintering additive, an additive manufacturing feedstock powder, organic additives and a carrier fluid to form a first mixture; (b) spraying the first mixture to form droplets, wherein each droplet comprises carrier fluid, organic additive, sintering additive, and additive manufacturing feedstock powder; and (c) heating the droplets to evaporate the carrier fluid from the droplets and form a powder mixture comprising sintering additive particles, additive manufacturing feedstock powder particles, and organic additive;

[00038] In some embodiments, the method further comprises: (a) depositing a first layer of the powder mixture onto a surface (e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; and (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article.

[00039] In some embodiments, the method further comprises heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article.

[00040] In some embodiments, the method further comprises heating the additively manufactured article to a second temperature for a sufficient time to form a final additively manufactured article (e.g., density ing the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[00041] In some embodiments, the carrier fluid includes but is not limited to: water and ethanol.

[00042] In some embodiments, organic additives include but are not limited to: polyvinylalcohol, polyethylene glycol, and paraffins. [00043] In some embodiments, the first mixture is a slurry. In some embodiments, the slurry is 15 wt. % to 35 wt. % carrier fluid, 1.0 wt. % to 5.0 wt. % organic additives and the balance sintering additive and additive manufacturing feedstock powder. As used herein, the term“slurry” means a composition in which solids and liquid are present in separate phases.

[00044] In some embodiments, the fluid weight of the slurry can vary depending on the density of the additive manufacturing feedstock powder and sintering additive.

[00045] In some embodiments, the sintering additive comprises a single element (e.g. iron). In some embodiments, the sintering additive comprises multiple elements (e.g. iron boride), which multiple elements may be in elemental or compound form. In some embodiments, the sintering additive is magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron boride (FeB, Fe ₂ B), silicon boride (S1B3, S1B4), boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), yttrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe), or combinations thereof.

[00046] In some embodiments, the D50 of the sintering additive is not greater than 20 microns.

[00047] In some embodiments, the D50 of the sintering additive is from 0.05 microns to 5 microns.

[00048] In some embodiments, the additive manufacturing feedstock powder comprises metal, metal alloys, metal oxides, non-oxides (e.g., borides, carbides, nitrides), or combinations thereof.

[00049] In some embodiments, the D50 of the powder mixture is not greater than 200 microns.

[00050] In some embodiments, the D50 of the powder mixture is from 1 micron to 200 microns. [00051] In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 5.0 wt. %.

[00052] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 5.0 wt. %.

[00053] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. %.

[00054] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 1.0 wt. %.

[00055] In one aspect of the disclosure a method is provided, comprising: (a) depositing a first layer of an additive coated powder onto a deposition surface, wherein the additive coated powder comprises an additive manufacturing feedstock powder, wherein the additive manufacturing feedstock powder comprises a coating, wherein the coating comprises a sintering additive; (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and additive coated powder; and; (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article, wherein, the surface is one of : a previously bound layer of binder fluid and additive coated powder or a build substrate of a binder jet 3D printing apparatus.

[00056] In some embodiments, the method further comprises heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article.

[00057] In some embodiments, the method further comprises heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article (e.g., densifying the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[00058] In some embodiments, the additive manufacturing feedstock powder particles are completely coated with the sintering additive (e.g., the additive manufacturing feedstock powder particles are enclosed within the sintering additive).

[00059] In some embodiments, additive manufacturing feedstock powder particles are partially coated with the sintering additive.

[00060] In some embodiments, some additive manufacturing feedstock powder particles are completely coated with the sintering additive, and some additive manufacturing feedstock powder particles are partially coated with the sintering additive.

[00061] In some embodiments, the additive manufacturing feedstock powder comprises metal, metal alloys, metal oxides, non-oxides (e.g., borides, carbides, nitrides), or combinations thereof.

[00062] In some embodiments, the sintering additive comprises a single element (e.g. iron). In some embodiments, the sintering additive comprises multiple elements (e.g. iron boride), which multiple elements may be in elemental or compound form. In some embodiments, the sintering additive is magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron boride (FeB, Fe ₂ B), silicon boride (S1B3, S1B4), boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), yttrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe), or combinations thereof.

[00063] In some embodiments, coating the additive manufacturing feedstock powder with the sintering additive further comprises chemically reacting the additive manufacturing feedstock powder with the sintering additive.

[00064] In some embodiments, coating the additive manufacturing feedstock powder with the sintering additive further comprises: depositing the sintering additive onto the additive manufacturing feedstock powder via a chemical vapor deposition process or a physical vapor deposition process.

[00065] In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 5.0 wt. %.

[00066] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 to 5.0 wt. %.

[00067] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. %.

[00068] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 to 1.0 wt. %.

[00069] In one aspect of the disclosure an apparatus is provided, comprising: (a) a first material storage unit configured to (i) store an additive manufacturing feedstock powder and (ii) deposit the additive manufacturing feedstock powder; (b) a second material storage unit configured to (i) store an sintering additive and (ii) deposit the sintering additive; (c) a deposition surface configured to receive the additive manufacturing feedstock powder from the first material storage unit and configured to receive the sintering additive from the second material storage unit; and (d) a binder fluid dispenser configured to (i) deposit a binder fluid onto at least one of: (a) the deposition surface, (b) a deposited additive manufacturing feedstock powder, and (c) a deposited sintering additive.

[00070] In some embodiments, the surface is a build platform of a binder j et 3D printing apparatus.

[00071] In some embodiments, the surface is a prior layer of the additive manufacturing feedstock powder and the sintering additive.

[00072] In some embodiments, the additive manufacturing feedstock powder comprises metal, metal alloys, metal oxides, non-oxides (e.g., borides, carbides, nitrides), or combinations thereof. [00073] In some embodiments, the sintering additive comprises a single element (e.g. iron). In some embodiments, the sintering additive comprises multiple elements (e.g. iron boride), which multiple elements may be in elemental or compound form. In some embodiments, the sintering additive is magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron boride (FeB, Fe ₂ B), silicon boride (S1B3, S1B4), boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), yttrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe, or combinations thereof.

[00074] In one aspect of the disclosure a method is provided, comprising: (a) depositing a first layer of a powder mixture onto a deposition surface (e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus), wherein the powder mixture comprises a boron-containing material and an additive manufacturing feedstock powder; (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article.

[00075] In one aspect of the disclosure a method is provided, comprising: (a) heating a metal alloy to form a molten metal alloy; (b) mixing a boron containing material and the molten metal alloy to form a molten metal alloy mixture; (c) forming liquid droplets of the molten metal alloy mixture; (d) cooling the liquid droplets to form a powder comprising the metal alloy and the additive, wherein the powder mixture has a D50 of not greater than 200 microns.

[00076] In some embodiments, the method further comprises: (a) depositing a first layer of the powder onto a surface (e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder; (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article.

[00077] In one aspect of the disclosure a method is provided, comprising: (a) mixing a boron containing material, an additive manufacturing feedstock powder, organic additives and a carrier fluid to form a first mixture; (b) spraying the first mixture to form droplets, wherein each droplet comprises carrier fluid, organic additive, additive containing powder, and additive manufacturing feedstock powder; (c) heating the droplets to evaporate the carrier fluid from the droplets and form a powder mixture comprising boron containing material particles, additive manufacturing feedstock powder particles, and organic additive.

[00078] In some embodiments, the method further comprises: (a) depositing a first layer of the powder mixture onto a surface (e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; and (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article.

[00079] In one aspect of the disclosure, a method is provided, comprising: (a) depositing a first layer of an additive coated powder onto a deposition surface, wherein the additive coated powder comprises an additive manufacturing feedstock, wherein the additive manufacturing feedstock comprises a coating, wherein the coating comprises a boron containing material ; (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid, boron containing material, and additive manufacturing feedstock powder; and (c) repeating steps (a)- (b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of the final additively manufactured article, wherein, the surface is a previously bound layer of binder fluid , boron containing material, and additive manufacturing feedstock powder or a build substrate of a binder jet 3D printing apparatus.

[00080] In one aspect of the disclosure a method is provided, comprising: (a) depositing a layer of an additive manufacturing feedstock powder onto a surface (e.g., a previously bound layer of binder fluid and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a mixture onto the layer of additive manufacturing feedstock powder, wherein the mixture comprises a binder fluid and a boron containing material, wherein depositing the mixture forms a first bound layer of binder fluid, boron containing material, and additive manufacturing feedstock powder; (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the boron containing material is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article.

[00081] In one aspect of the disclosure a method is provided, comprising: (a) depositing a layer of an additive manufacturing feedstock powder onto a surface (e.g., a previously bound layer of binder fluid, sintering additive, and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a mixture onto the layer of additive manufacturing feedstock powder, wherein the mixture comprises a sintering additive and a binder fluid, wherein the mixture comprises from 0.03 vol. % to 41 vol. % of the sintering additive, wherein the balance is binder fluid, wherein depositing the mixture forms a first bound layer of binder fluid, sintering additive, and additive manufacturing feedstock powder; (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article, wherein the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 5.0 wt. %. [00082] In one aspect of the disclosure a method is provided, comprising: (a) depositing a layer of an additive manufacturing feedstock powder onto a surface (e.g., a previously bound layer of binder fluid, sintering additive, and powder or a build substrate of a binder jet 3D printing apparatus); (b) depositing a mixture onto the layer of additive manufacturing feedstock powder, wherein the mixture comprises a sintering mixed with a binder fluid, wherein the mixture comprises from 0.01 vol. % to 32 vol. % of the sintering additive and the balance is binder fluid, wherein depositing the mixture forms a first bound layer of binder fluid, sintering additive, and additive manufacturing feedstock powder; (c) repeating steps (a)-(b) to build an additively manufactured article, wherein the sintering additive is configured to improve physical properties (e.g., at least one of improve densification, lower porosity, lower impurities, and improve homogeneity) of a final additively manufactured article, wherein the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. %.

[00083] In some embodiments, the mixture of binder fluid and sintering additive is deposited onto an entire surface of the additive manufacturing feedstock powder (e.g. the mixture is not selectively deposited onto the surface of the additive manufacturing feedstock powder). In some embodiments, the mixture of binder fluid and sintering additive is deposited onto the additive manufacturing feedstock powder without first determining the local density of the additive manufacturing feedstock powder.

[00084] In some embodiments, the method further comprises heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article. In some embodiments, the method further comprises heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article (e.g., densifying the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density). In some embodiments, the sintering additive does not melt at the second temperature.

[00085] The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[00086] Among those benefits and improvements that have been disclosed, other obj ects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.

[00087] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases“in one embodiment” and“in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though they may. Furthermore, the phrases“in another embodiment” and“in some other embodiments” as used herein do not necessarily refer to a different embodiment, although they may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[00088] In addition, as used herein, the term“or” is an inclusive“or” operator, and is equivalent to the term“and/or,” unless the context clearly dictates otherwise. The term“based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references, unless the context clearly dictates otherwise. The meaning of“in” includes“in” and“on”, unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

[00089] Embodiments of the present invention, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the invention depicted in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[00090] Figure 1 is a flowchart of an exemplary method in accordance with some embodiments of the present disclosure.

[00091] Figure 2 is a flowchart of an exemplary method in accordance with some embodiments of the present disclosure.

[00092] Figure 3 is a flowchart of an exemplary method in accordance with some embodiments of the present disclosure.

[00093] Figure 4 is a flowchart of an exemplary method in accordance with some embodiments of the present disclosure.

[00094] Figure 5 is a schematic drawing of an additive manufacturing binder jet printing system in accordance with some embodiments of the present disclosure.

[00095] Figure 6 is a flowchart of an exemplary method in accordance with some embodiments of the present disclosure.

[00096] The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION [00097] The present invention will be further explained with reference to the attached drawings. The drawings shown are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the present invention. Further, some features may be exaggerated to show details of particular components.

[00098] The figures constitute a part of this specification and include illustrative embodiments of the present invention and illustrate various objects and features thereof. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[00099] Among those benefits and improvements that have been disclosed, other obj ects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples is given in connection with the various embodiments of the invention, which are intended to be illustrative, and not restrictive.

[000100] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases“in one embodiment” and“in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though it may. Furthermore, the phrases“in another embodiment” and“in some other embodiments” as used herein do not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention. [000101] The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on".

[000102] As used herein,“additive manufacturing” means“a process of j oining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies”, as defined in ASTM F2792-l2a entitled “Standard Terminology for Additively Manufacturing Technologies”. Non-limiting examples of additive manufacturing processes useful in producing crack-free aluminum alloy products include, for instance, DMLS (direct metal laser sintering), SLM (selective laser melting), SLS (selective laser sintering), and EBM (electron beam melting), among others. Any suitable feedstocks may be used, including one or more powders, one or more wires, and combinations thereof. In some embodiments the additive manufacturing feedstock is comprised of one or more powders. Shavings are types of particles. In some embodiments, the additive manufacturing feedstock is comprised of one or more wires. A ribbon is a type of wire.

[000103] In one embodiment, the additive manufacturing comprises binder jet 3D printing. As used herein,“binder jet 3D printing” is the spreading of a layer of feedstock material (e.g., particulate layer), and then selectively jet-printing a fluid onto the layer of feedstock material to cause the selected portions of the particulate layer to bind together. This sequence is repeated for additional layers until the desired part has been constructed. Post build processes include but are not limited to: heating or processing the part to cure the binder and/or generate some rigidity in the part to create a green article that have limited relative green (as printed) densities due to inherent porosity in the powder bed yielding the article. Thus, a method of overcoming the low/limited green densities through enhanced sintering is required to produce useful articles. [000104] As used herein, a“particle” means a distinct fragment of matter. A particle may be produced, for example, via gas atomization. A particle may be jagged or spherical. A jagged particle may be spherodized by any suitable known process. A particle may be of any suitable size, including of a size suitable for use in an additive manufacturing environment, as well as very small (e.g., fines) or very large (e.g., chips) fragments of matter.

[000105] As used herein,“powder” means a material comprising particles suited to produce an alloy product via additive manufacturing. In one embodiment, a powder includes metal particles. In one embodiment, a powder includes metal alloy particles. In one embodiment, a powder includes metal particles and metal alloy particles. In any of these embodiments, the powder may optionally include other particles, as defined below.

[000106] As used herein, "particle size distribution" refers to the relative amounts of particles present, sorted according to the number of sizes present. Particle size distribution may be defined in one or more ways. For example, a Dio of 7 microns means that 10% of the particles are smaller than about 7 microns while 90% of the particles are equal to or greater than about 7 microns. As another example, a D50 of 12 microns means that half of the particles are smaller than about 12 microns while the other half are equal to or greater than about 12 microns, and D90 of 20 microns means that 90% of the particles are smaller than about 20 microns while 10% of the particles are equal to or greater than about 20 microns. Generally, in referencing the same material, the particle size distributions of Dio to D90 will be ascending (i.e. D90 values are larger than both D50 and Dio values, while D50 values are larger than Dio values). Although Dio, D50, and D90 are referenced herein, it is readily recognized that in measuring particle size, the PSD may be any PSD that is useful, and is not limited to Dio, D50, and D90 values.

[000107] As used herein,“sintering” is a densification method where an article is heated to temperatures below the melting point or liquidus temperature of the major volume component of a material system to thermally induce mass transport resulting in the removal of porosity. The extent of sintering is measured in relative density.

[000108] As used herein, an“article” is a part or a shape comprised of a specific combination of materials in a specific shape. The article can have compositions comprised of major material components (e.g., greater than 50% by volume) and minor material components (e.g., less than 50% by volume).

[000109] As used herein,“relative density” is the bulk density of a material (e.g., mass of article divided by total volume, including volume of pores within the article) divided by the theoretical density of the material system multiplied by 100 (i.e. ratio of actual to theoretical density expressed in percent of theoretical density).

[000110] As used herein,“densify” or“densification” refers to the removal of porosity from an article comprised of particulate material held together by weak interparticle forces, binders, and material bridges. A certain percent of the porosity of the article is dictated by material packing.

[000111] As used herein, a“sintering aid” is a functional additive. In some embodiments, the sintering additive may improve and/or enhance the performance of at least one or more of the non-limiting examples of densifying mechanisms: (a) increasing mass transport via liquid phase sintering (e.g., dissolution of major component in a liquid, and re-precipitate upon cooling in pore space now filled by liquid) wherein the liquid phase is different in composition from the major material component; (b) increasing mass transport via solid state diffusion (e.g. through increased defect concentration within the material lattice); (c) yielding improved densification (e.g. densification at a lower sintering temperature, a reduced sintering time requirement, and/or resulting in substantially less residual porosity for a predetermined amount of time at a predetermined temperature compared to the same material without sintering aid additions. [000112] In some embodiments of the present disclosure, one or more sintering aids are physically blended with an additive manufacturing feedstock. In some embodiments, physical blending includes but is not limited to: (a) mechanical blending of specific material ratios (e.g., the ratio comprising a major feedstock component, a minor feedstock component, and a sintering aid component); (b) at least partially coating a feedstock material; (c) agglomeration of blended materials. In some embodiments of the present disclosure, one or more sintering aids are mixed with a binder solution (e.g., forming a suspension) and jetted into an additive manufacturing feedstock bed. In some embodiments of the present disclosure, one or more sintering aids are introduced to additive manufacturing feedstock via alloy or solid solution chemistry modification. In some embodiments of the present disclosure, metal alloy powders with sintering aids include but are not limited to: titanium based alloys, aluminum based alloys, nickel based alloys, cobalt based alloys, iron based alloys, copper based alloys, molybdenum based alloys, and combinations thereof. In some embodiments of the present disclosure, ceramic alloy powders with sintering aids include but are not limited to: metal oxide ceramics (e.g., M2O3, MO2, MO), phosphate based ceramics (e.g., hydroxyapatite), non-oxide ceramics (e.g., borides, carbides, nitrides), hybrid oxy-carbide or oxy-nitride ceramics, and combinations thereof.

[000113] Figure 1 is a flowchart of an exemplary method 100 in accordance with some embodiments of the present disclosure. In some embodiments, method 100 may include mixing 102 a sintering additive with the additive manufacturing feedstock powder to form a powder mixture. Method 100 may include first depositing 104 a first layer of the powder mixture onto a surface. Method 100 may include second depositing 106 a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture. Method 100 may include repeating 108 steps 104-106 to build an additively manufactured article. In some embodiments, the exemplary methods described herein are performed on an additive manufacturing binder jet printing system (e.g., an exemplary additive manufacturing binder jet printing system described below with respect to Figure 5).

[000114] In some embodiments, the additive manufacturing feedstock has a D50 of not greater than 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of not greater than 150 microns. In some embodiments, the additive manufacturing feedstock has a D50 of not greater than 100 microns. In some embodiments, the additive manufacturing feedstock has a D50 of not greater than 50 microns. In some embodiments, the additive manufacturing feedstock has a D50 of not greater than 25 microns.

[000115] In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 20 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 40 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 60 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 80 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 100 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 120 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 140 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 160 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 180 microns to 200 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 180 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 160 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 140 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 120 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 100 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 80 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 60 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 40 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 1 micron to 20 microns.

[000116] In some embodiments, the additive manufacturing feedstock has a D50 of from 10 microns to 60 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 20 microns to 60 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 30 microns to 60 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 40 microns to 60 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 50 microns to 60 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 10 microns to 50 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 10 microns to 40 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 10 microns to 30 microns. In some embodiments, the additive manufacturing feedstock has a D50 of from 10 microns to 20 microns.

[000117] In some embodiments, an additive manufacturing feedstock is mixed with a sufficient amount of a sintering additive to form a powder mixture. In some embodiments, the additive manufacturing feedstock powder includes but is not limited to: metal, metal alloys, metal oxides, non-oxides (e.g., borides, carbides, nitrides), or combinations thereof. In some embodiments, the metal alloy is one of a titanium-based alloy, an aluminum-based alloy, a nickel-based alloy, a cobalt-based alloy, an iron-based alloy, a copper-based alloy, and a molybdenum-based alloy. In some embodiments, suitable additive manufacturing feedstock powder includes but is not limited to: Ti64, and Ti-48Al-2Cr-2Nb. In some embodiments, a suitable additive manufacturing feedstock powder is a titanium-based alloy comprising, 4.5 to 7.5 wt. % aluminum, 2.0 to 8.0 wt. % tin, 1.5 to 6.5 wt. % niobium, 0.1 to 2.5 wt. % molybdenum, and 0.1 to 0.6 wt. % silicon, as described in United States Patent No. 9,957,836, entitled,“Titanium Alloy Having Good Oxidation Resistance and High Strength at Elevated Temperatures,” issued May 1, 2018.

[000118] In some embodiments, a sintering additive (e.g., an additive containing powder) is mixed with the additive manufacturing feedstock powder to form a powder mixture. In some embodiments, the sintering additive includes but is not limited to: magnesium (Mg), boron (B), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron boride (FeB, Fe ₂ B), silicon boride (S1B3, S1B4), boric oxide (B ₂ 03), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), ytrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe), or combinations thereof. In some embodiments, a first layer of the powder mixture is deposited onto a surface.

[000119] In some embodiments, a binder fluid is deposited onto the first layer to form a first bound layer of binder fluid and powder mixture. In some embodiments, non-limiting examples of suitable binder fluid include but are not limited to: acrylonitrile butadiene styrene, polyamide, and polycarbonate. In some embodiments, commercially available binder jet compatible binders are contemplated for use herein, in conjunction with one or more of the aforementioned embodiments. In some embodiments, non-limiting examples of commercially available binders may be procured from ExOne and may include a furan binder, a phenolic binder, a silicate binder and an aqueous-based binder. The list of suitable binder fluid is exemplary, and other suitable binder fluids not listed herein may be used. In some embodiments, the surface is a build platform of an additive manufacturing binder jet printing system. In some embodiments, the surface is a prior bound layer.

[000120] In some embodiments, depositing the first layer and depositing the binder fluid is repeated to build an additive manufactured article. For example, in some embodiments, a second layer of the powder mixture is deposited onto the first deposited layer. In some embodiments, the binder fluid is deposited onto the second layer to form the second bound layer. [000121] In some embodiments, the additively manufactured article is heated to a first sufficient temperature for a sufficient time to remove the binder from the additively manufactured article. In some embodiments, the additively manufactured article is heated to a second sufficient temperature for a sufficient time to form a final additively manufactured article (e.g., densifying the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[000122] In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 4.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 4.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 3.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 2.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 2.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 1.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of not greater than 1.0 wt. %.

[000123] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.5 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 1.0 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 2.0 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 3.0 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 4.0 wt. % to 5.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 4.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 3.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 2.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 0.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.03 wt. % to 0.1 wt. %.

[000124] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.5 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 1.0 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 1.5 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 2.0 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 2.5 wt. % to 3.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 2.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 2.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 1.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 0.5 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 0.1 wt. %.

[000125] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.3 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.5 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.7 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.9 wt. % to 1.0 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 0.8 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 0.6 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 0.4 wt. %. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 0.2 wt. %.

[000126] In some embodiments, the sintering additive acts as a sintering aid to improve the sintering process, for example, by lowering the temperature necessary for sintering, or lowering the time it takes to sinter. In some embodiments, the sintering additive acts as a particle packing facilitator to fill in the pores of the unsintered additively manufactured article and improve the density of the unsintered additively manufactured article. In some embodiments, the sintering additive acts as a densification enhancer to improve the density of the sintered additively manufactured article, for example, by improving diffusion in the powder bed. In some embodiments, the sintering additive acts as an impurity scavenger to improve, for example, the properties of the sintered additively manufactured article (e.g., density). In some embodiments, non-limiting examples of impurities include oxygen and chlorine, which form gas pockets in the unsintered additively manufactured article. In some embodiments, the gas pockets can lead to increased porosity and/or lower homogeneity in the sintered additively manufactured article. In some embodiments, the impact of the sintering additive as an impurity scavenger can be identified via chemical analysis, metallography, and/or spectroscopy of the sintered additively manufactured article. In some embodiments, the sintered additively manufactured article can be examined for improvements in physical properties, for example, via at least one of stress testing, fatigue testing, tensile testing, and combinations thereof.

[000127] In some embodiments, the additives used in the exemplary methods described herein facilitate densification of the powders into the sintered additively manufactured article (e.g., final additively manufactured article). In one embodiment, the selected metal additive is a boron containing additive which produces a sintered additively manufactured article that has a density of from about 73% to about 99% of its theoretical density. A theoretical density (ptheory) is the highest density that a material could achieve as calculated from the atomic weight and crystal structure.

(ptheory) = N _c A/V _c N _a

[000128] Where: N _c =number of atoms in unit cell, A=Atomic Weight [kg mol ' |. Vc=Volume of unit cell [m ³ ], and N _a =Avogadro's number [atoms mol ^-1 ].

[000129] Figure 2 is a flowchart of an exemplary method 200 in accordance with some embodiments of the present disclosure. In some embodiments, method 200 may include heating 202 the metal alloy or materials to form a molten metal alloy. Method 200 may include mixing 204 a sintering additive and the molten metal alloy to form a molten metal alloy mixture. Method 200 may include forming 206 liquid droplets of the mixed molten metal alloy. Method 200 may include cooling 208 the liquid droplets to form a powder mixture comprising the metal alloy and the sintering additive. Method 200 may include first depositing 210 a first layer of the powder mixture onto a surface. Method 200 may include second depositing 214 a binder fluid onto the first layer to form a first bound layer of binder fluid and powder. Method 200 may include repeating 214 steps 210-212 to build an additively manufactured article.

[000130] In some embodiments, the metal alloy is heated to form a molten metal alloy. In some embodiments, the metal alloy is titanium based alloys, aluminum based alloys, nickel based alloys, cobalt based alloys, iron based alloys, copper based alloys, molybdenum based alloys, and combinations thereof. In some embodiments, suitable metal alloys include but are not limited to: Ti64, and Ti-48Al-2Cr-2Nb. In some embodiments, the molten metal alloy has a sintering additive content of not greater than 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of not greater than 4.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of not greater than 3.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of not greater than 2.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of not greater than 1.0 wt. %.

[000131] In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.1 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.5 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 1.0 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 2 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 3.0 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 4.0 wt. % to 5.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 4.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 3.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 2.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 1.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 0.5 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.03 wt. % to 0.1 wt. %.

[000132] In some embodiments, the molten metal alloy has a sintering additive content of from 0.1 wt. % to 1.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.3 wt. % to 1.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.5 wt. % to 1.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.7 wt. % to 1.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.9 wt. % to 1.0 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.1 wt. % to 0.8 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.1 wt. % to 0.6 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.1 wt. % to 0.4 wt. %. In some embodiments, the molten metal alloy has a sintering additive content of from 0.1 wt. % to 0.2 wt. %.

[000133] In some embodiments, a sintering additive and the molten metal alloy are mixed to form a mixed molten metal alloy. Non-limiting examples of suitable sintering additive are provided in exemplary method 100. In some embodiments, liquid droplets of the mixed molten metal alloy are formed (e.g., via forcing the mixed molten metal alloy through an orifice at sufficiently high velocity to ensure turbulent flow). In some embodiments, the liquid droplets are cooled to form a powder comprising the metal alloy and the additive. In some embodiments, the liquid droplets of the mixed molten metal alloy are cooled into particles. In some embodiments, the gases used in the atomization process are cooler than the liquid droplets of the mixed molten metal alloy and thus actively cool the liquid droplets of the mixed molten metal alloy. In some embodiments, the atomizing tower is designed to be large enough to cool the liquid droplets of the mixed molten metal alloy into solid particles before reaching the bottom of the atomizing tower.

[000134] In some embodiments, the powder mixture (i.e. additive manufacturing feedstock powder mixed with sintering additive powder) comprises particles. In some embodiments, the mixture has a D50 of not greater than 200 microns. In some embodiments, the mixture has a D50 of not greater than 150 microns. In some embodiments, the mixture has a D50 of not greater than 100 microns. In some embodiments, the mixture has a D50 of not greater than 50 microns. In some embodiments, the mixture has a D50 of not greater than 25 microns.

[000135] In some embodiments, the mixture has a D50 of from 1 micron to 200 microns. In some embodiments, the mixture has a D50 of from 20 microns to 200 microns. In some embodiments, the mixture has a D50 of from 40 microns to 200 microns. In some embodiments, the mixture has a D50 of from 60 microns to 200 microns. In some embodiments, the mixture has a D50 of from 80 microns to 200 microns. In some embodiments, the mixture has a D50 of from 100 microns to 200 microns. In some embodiments, the mixture has a D50 of from 120 microns to 200 microns. In some embodiments, the mixture has a D50 of from 140 microns to 200 microns. In some embodiments, the mixture has a D50 of from 160 microns to 200 microns. In some embodiments, the mixture has a D50 of from 180 microns to 200 microns. In some embodiments, the mixture has a D50 of from 1 micron to 180 microns. In some embodiments, the mixture has a D50 of from 1 micron to 160 microns. In some embodiments, the mixture has a D50 of from 1 micron to 140 microns. In some embodiments, the mixture has a D50 of from 1 micron to 120 microns. In some embodiments, the mixture has a D50 of from 1 micron to 100 microns. In some embodiments, the mixture has a D50 of from 1 micron to 80 microns. In some embodiments, the mixture has a D50 of from 1 micron to 60 microns. In some embodiments, the mixture has a D50 of from 1 micron to 40 microns. In some embodiments, the mixture has a D50 of from 1 micron to 20 microns.

[000136] In some embodiments, the mixture has a D50 of from 10 microns to 60 microns. In some embodiments, the mixture has a D50 of from 20 microns to 60 microns. In some embodiments, the mixture has a D50 of from 30 microns to 60 microns. In some embodiments, the mixture has a D50 of from 40 microns to 60 microns. In some embodiments, the mixture has a D50 of from 50 microns to 60 microns. In some embodiments, the mixture has a D50 of from 10 microns to 50 microns. In some embodiments, the mixture has a D50 of from 10 microns to 40 microns. In some embodiments, the mixture has a D50 of from 10 microns to 30 microns. In some embodiments, the mixture has a D50 of from 10 microns to 20 microns. In some embodiments, the mixture has a bimodal size distribution.

[000137] In some embodiments, a first layer of the powder is deposited onto a deposition surface (e.g., a build platform of an additive manufacturing binder jet printing system or a prior bound layer). In some embodiments, a binder fluid is deposited onto the first layer to form a first bound layer. Non-limiting examples of suitable binder fluids are provided in exemplary method 100. In some embodiments, depositing the first layer and depositing the binder fluid is repeated to build an additive manufactured article. For example, in some embodiments, a second layer of the powder mixture is deposited onto the first bound layer. In some embodiments, the binder fluid is deposited onto the second layer to form the second bound layer. Exemplary additive content ranges for the sintered additively manufactured article are provided in exemplary method 100.

[000138] In some embodiments, the additively manufactured article is heated to a first sufficient temperature for a sufficient time to remove the binder fluid from the additively manufactured article. In some embodiments, the additively manufactured article is heated to a second sufficient temperature for a sufficient time to form a final additively manufactured article (e.g., densifying the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[000139] In some embodiments, finer (e.g., not greater than 20-micron) spherical and/or non-spherical metal powders are agglomerated (non-melting methods) into a form that can be easily spread, packed and layered to form a powder bed suitable for a binder jet additive manufacturing process. Such agglomerates can be comprised of metal powders and additive particles or chemicals to form an engineered powder system conducive to enhanced sintering. The agglomerates can be formed by methods including but not limited to: wet mixing and spray drying, rotary ball forming methods, and colloidal and gelation agglomeration/ball forming methods with appropriate organic additives. The organic components of the agglomeration process can be combined with binder jet chemicals to form a chemical -jet binder system.

[000140] Figure 3 is a flowchart of an exemplary method 300 utilizing spray drying in accordance with some embodiments of the present disclosure. In some embodiments, the method 300 begins at 302 by mixing an additive containing powder, an additive manufacturing feedstock powder, an organic additive, and a carrier fluid to form a first mixture. In some embodiments, non-limiting examples of the carrier fluid include water and alcohol. Non- limiting examples of suitable additive containing powders and additive manufacturing feedstock powders are provided in exemplary method 100. Non-limiting examples of suitable organic additives include polyvinylalcohol, polyethylene glycol and paraffins. Method 300 may include spraying 304 the first mixture to form droplets. Method 300 may include heating 306 the droplets to form a dry powder mixture. Method 300 may include first depositing 308 a first layer of the powder mixture onto a surface. Method 300 may include second depositing 310 a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture. Method 300 may include repeating 312 steps 308-310 to build and additively manufactured product. [000141] In some embodiments, the sintering additive has a D50 of not greater than 20 microns. In some embodiments, the sintering additive has a D50 of not greater than 15 microns. In some embodiments, the sintering additive has a D50 of not greater than 10 microns. In some embodiments, the sintering additive has a D50 of not greater than 5 microns.

[000142] In some embodiments, the sintering additive has a D50 of fromO.05 microns to 50 microns. In some embodiments, sintering additive has a D50 of from 0.1 microns to 50 microns. In some embodiments, the sintering additive has a D50 of from 0.5 microns to 50 microns. In some embodiments, the sintering additive has a D50 of from 1 micron to 50 microns. In some embodiments, the sintering additive has a D50 of from 10 microns to 50 microns. In some embodiments, the sintering additive has a D50 of from 20 microns to 50 microns. In some embodiments, the sintering additive has a D50 of from 30 microns to 50 microns. In some embodiments, the sintering additive has a D50 of from 40 microns to 50 microns. In some embodiments, the sintering additive has a D50 of from 0.05 microns to 40 microns. In some embodiments, the sintering additive has a D50 of from 0.05 microns to 30 microns. In some embodiments, the sintering additive has a D50 of from 0.05 microns to 20 microns. In some embodiments, the sintering additive has a D50 of from 0.05 microns to 10 microns. In some embodiments, the sintering additive has a D50 of from 0.05 microns to 1 micron.

[000143] In some embodiments, the first mixture is sprayed to form droplets. In some embodiments, the droplets are heated to a temperature sufficient to evaporate the carrier fluid from the droplets and form a powder mixture. In some embodiments, the organic additives act as binders to hold the droplet together after drying. In some embodiments, the powder mixture comprises additive containing powder particles, additive manufacturing feedstock powder particles, and organic additive.

[000144] In some embodiments, a first layer of the powder is deposited onto a surface (e.g., a build platform of an additive manufacturing binder jet printing system or a prior bound layer). In some embodiments, a binder fluid is deposited onto the first layer to form a first bound layer. Non-limiting examples of suitable binder fluids are provided in exemplary method 100. Exemplary additive content ranges for the final additively manufactured article are provided in exemplary method 100.

[000145] In some embodiments, the additively manufactured article is heated to a first sufficient temperature for a sufficient time to remove the binder fluid from the additively manufactured article. In some embodiments, the additively manufactured article is heated to a second sufficient temperature for a sufficient time to form a final additively manufactured article (e.g., densifying the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density).

[000146] Figure 4 is a flowchart of an exemplary method 400 in accordance with some embodiments of the present disclosure. Method 400 may include coating 402 an additive manufacturing feedstock powder with a sintering additive to form an additive coated powder. Method 400 may include first depositing 404 a first layer of the powder mixture onto a surface. Method 400 may include second depositing 406 a binder fluid onto the first layer to form a first bound layer of binder fluid and additive coated powder. Method 400 may include repeating 408 steps 406-408 to build an additively manufactured article.

[000147] In some embodiments, an additive manufacturing feedstock powder is coated with a sintering additive to form an additive coated powder. Non-limiting examples of suitable sintering additives and additive manufacturing feedstock powders are provided in exemplary method 100. In some embodiments, the additive manufacturing feedstock powder is coated with the sintering additive by chemically reacting the additive manufacturing feedstock powder with the sintering additive. In some embodiments, the sintering additive is coated onto a surface of the additive manufacturing feedstock powder via a chemical vapor deposition process (e.g., exposing the additive manufacturing feedstock to volatile precursors containing the additive materials which react and/or decompose on the surface of the additive manufacturing feedstock powders) or a physical vapor deposition process (e.g., sputter deposition wherein the coating material is ejected from a target via a sputtering gas). In some embodiments, physical coating methods include but are not limited to: physical vapor deposition, sputtering, electrostatic condensation, and vaporization condensation. In some embodiments, chemical coating methods include chemical vapor deposition and sol gel.

[000148] In some embodiments, a first layer of the powder is deposited onto a deposition surface (e.g., a build platform of an additive manufacturing binder jet printing system or a prior bound layer). In some embodiments, a binder fluid is deposited onto the first layer to form a first bound layer. Non-limiting examples of suitable binder fluids are provided in exemplary method 100. In some embodiments, depositing the first layer and depositing the binder fluid is repeated to build an additive manufactured article. For example, in some embodiments, a second layer of the powder mixture is deposited onto the first deposited layer. In some embodiments, the binder fluid is deposited onto the second layer to form the second bound layer.

[000149] In some embodiments, the additively manufactured article is heated to a first sufficient temperature for a sufficient time to remove the binder from the additively manufactured article. In some embodiments, the additively manufactured article is heated to a second sufficient temperature for a sufficient time to form a final additively manufactured article (e.g., density ing the green form having a first relative density into a final additively manufactured article having a second relative density, wherein the second relative density is greater than the first relative density). Exemplary additive content ranges for the sintered additively manufactured article are provided in exemplary method 100.

[000150] Figure 6 is a flowchart of an exemplary method 600 in accordance with some embodiments of the present disclosure. Method 600 may include mixing 602 a sintering additive with a binder fluid to form a mixture. Method 600 may include first depositing 604 a layer of additive manufacturing feedstock powder onto a surface. Method 600 may include second depositing 606 the mixture onto the additive manufacturing feedstock powder layer to form a first bound layer of binder fluid, sintering additive and powder mixture. Method 600 may include repeating 608 steps 604-606 to build an additively manufactured article.

[000151] In some embodiments, a sintering additive is mixed with a binder fluid to form a mixture of the binder fluid and the sintering additive. Non-limiting examples of suitable sintering additives and additive manufacturing feedstock powders are provided in exemplary method 100. Non-limiting examples of suitable binder fluids are provided in exemplary method 100

[000152] In some embodiments, a layer of an additive manufacturing feedstock powder is deposited onto a surface (e.g., a previously bound layer of binder fluid, sintering additive, and powder or a build substrate of a binder jet 3D printing apparatus). In some embodiments, the mixture is deposited onto the layer of additive manufacturing feedstock powder to form a first bound layer of binder fluid, sintering additive and additive manufacturing feedstock powder. In some embodiments, depositing the layer of additive manufacturing feedstock powder and depositing the mixture is repeated to build an additive manufactured article. For example, in some embodiments, a second layer of the additive manufacturing feedstock powder is deposited onto the first layer of additive manufacturing feedstock. In some embodiments, the mixture is deposited onto the second layer of additive manufacturing feedstock to form a second bound layer of binder fluid, sintering additive and additive manufacturing feedstock powder.

[000153] In some embodiments, the sintering additive is boron. In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. % and the binder mixture comprises from 0.05 vol. % to 26 vol. % boron and the balance is binder fluid. [000154] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 5.0 wt. % and the binder mixture comprises from 0.03 vol. % to 41 vol. % sintering additive and the balance is binder fluid.

[000155] In some embodiments, the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. % and the binder mixture comprises from 0.01 vol. % to 32 vol. % sintering additive and the balance is binder fluid.

[000156] Table 1, below, depicts a range of sintering additive concentrations (vol. %) in the binder fluid that may be used to produce a final additively manufactured article having a sintering additive content of from 0.1 wt. % to 5.0 wt. % in the final sintered part (i.e. after thermal processing/sintering). Exemplary concentration ranges were calculated based on the desired additive concentration in the final sintered part (e.g. from 0.1 wt. % to 5.0 wt. %). Various examples are provided in several different alloy feedstock‘bases’, which utilize different combinations of sintering additive.

Table 1: Alloy feedstock bases, sintering additives, and exemplary concentrations of sintering additives.

[000157] Table 2, below, depicts a range of sintering additive concentrations (vol. %) in the binder fluid that may be used to produce a final additively manufactured article having a sintering additive content of from 0.05 wt. % to 3.5 wt. % in the final sintered part (i.e. after thermal processing/sintering). Exemplary concentration ranges were calculated based on the desired additive content in the final sintered part (e.g. from 0.05 wt. % to 3.5 wt. %).

Table 2: Alloy feedstock bases, sintering additives, and exemplary concentrations of sintering additives.

[000158] Figure 5 is a schematic drawing of an additive manufacturing binder jet printing system 500 in accordance with some embodiments of the present disclosure. In some embodiments, the system 500 comprises a first material storage unit 502 (e.g., a first hopper) and a second material storage unit 504 (e.g., a second hopper). In some embodiments, the first material storage unit 502 stores an additive manufacturing feedstock powder. In some embodiments, the second material storage unit 504 stores a sintering additive. In some embodiments, the first material storage unit 502 deposits the additive manufacturing feedstock powder onto a surface 506 (e.g., a build platform of an additive manufacturing binder jet printing system or a prior bound layer) via one or more passageways 508 (e.g., pipes, hoses) connecting the first material storage unit 502 to the surface 506. In some embodiments, the second material storage unit 504 deposits the sintering additive onto a surface 508 via one or more passageways 508 (e.g., pipes, hoses) connecting the second material storage unit 504 to the surface 506. In some embodiments, the apparatus 500 comprises a binder fluid dispenser 510. In some embodiments, binder fluid dispenser 510 deposits a binder fluid onto a deposited additive manufacturing feedstock powder and/or sintering additive.

[000159] In some embodiments, the additive manufacturing feedstock powder and sintering additive are mixed prior to storing in the hopper (e.g., only one hopper needed in the system).

[000160] In some embodiments, the additive manufacturing feedstock powder, sintering additive, and the binder fluid can be deposited on the surface in any order. For example, in some embodiments, a layer of additive manufacturing feedstock powder and a layer of sintering additive are consecutively deposited onto the surface. A binder fluid can be deposited onto only the layer of additive manufacturing feedstock powder, onto only the layer of sintering additive, or onto both the layer of additive manufacturing feedstock powder and the layer of sintering additive.

[000161] In some embodiments, the additive manufacturing feedstock powder and sintering additive are concurrently deposited onto the surface, and a binder fluid is deposited atop the combined layer.

[000162] The products made by the process described herein may be used in a variety of product applications. In one embodiment, the products made by the process described herein are utilized in an elevated temperature application, such as in an aerospace or automotive vehicle. In one embodiment, the products made by the process described herein are utilized as an engine component in an aerospace vehicle (e.g., in the form of a blade, such as a compressor blade incorporated into the engine). In another embodiment, the products made by the process described herein are used as a heat exchanger for the engine of the aerospace vehicle. The aerospace vehicle including the engine component / heat exchanger may subsequently be operated. In one embodiment, the products made by the process described herein are an automotive engine component. The automotive vehicle including the engine component may subsequently be operated. For instance, the products made by the process described herein may be used as a turbo charger component (e.g., a compressor wheel of a turbo charger, where elevated temperatures may be realized due to recycling engine exhaust back through the turbo charger), and the automotive vehicle including the turbo charger component may be operated. In another embodiment, the products made by the process described herein may be used as a blade in a land based (stationary) turbine for electrical power generation, and the land based turbine included the alloy product may be operated to facilitate electrical power generation. In some embodiments, the products made by the process described herein are utilized in defense applications, such as in body armor, and armed vehicles (e.g., armor plating). In other embodiments, the products made by the process described herein are utilized in consumer electronic applications, such as in consumer electronics, such as, laptop computer cases, battery cases, cell phones, cameras, mobile music players, handheld devices, computers, televisions, microwaves, cookware, washers/dryers, refrigerators, and sporting goods, among others.

[000163] In another aspect, the products made by the process described herein are utilized in a structural application. In one embodiment, the products made by the process described herein are utilized in an aerospace structural application. For instance, the products made by the process described herein may be formed into various aerospace structural components, including floor beams, seat rails, fuselage framing, bulkheads, spars, ribs, longerons, and brackets, among others. In another embodiment, the products made by the process described herein are utilized in an automotive structural application. For instance, the products made by the process described herein may be formed into various automotive structural components including nodes of space frames, shock towers, and subframes, among others. In one embodiment, the products made by the process described herein are a body-in-white (BIW) automotive product.

[000164] In another aspect, the products made by the process described herein are utilized in an industrial engineering application. For instance, the products made by the process described herein may be formed into various industrial engineering products, such as tread- plate, tool boxes, bolting decks, bridge decks, and ramps, among others.

[000165] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.

[000166] Aspects of the invention will now be described with reference to the following numbered clauses:

1. A method comprising:

(a) depositing a first layer of a powder mixture onto a deposition surface, wherein the powder mixture comprises an additive manufacturing feedstock and a sintering additive;

(b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; and

(c) repeating steps (a)-(b) to build an additively manufactured article,

wherein the sintering additive is configured to improve physical properties of a final additively manufactured article.

2. The method of clause 1, wherein the sintering additive is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article. 3. The method of any of the preceding clauses, comprising:

heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article.

4. The method of any of the preceding clauses, comprising:

heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article.

5. The method of clause 4, wherein the heating comprises densifying the additively manufactured article, wherein the additively manufactured article comprises a first relative density and, wherein the final additively manufactured article comprises a second relative density, wherein the second relative density is greater than the first relative density.

6. The method of any of the preceding clauses, comprising at least one of: inspecting the final additively manufactured article, machining the final additively manufactured article, surface treating the final additively manufactured article, surface finishing of the final additively manufactured article, and cleaning the final additively manufactured article.

7. The method of any of the preceding clauses, wherein the additive manufacturing feedstock comprises at least one of a powder and a wire.

8. The method of any of the preceding clauses, wherein the additive manufacturing feedstock comprises at least one of: a metal, a metal alloy, a metal oxide, a non-oxide, a boride, a carbide, a nitride, and combinations thereof.

9. The method of any of the preceding clauses, wherein the additive manufacturing feedstock comprises one of: a titanium-based alloy, an aluminum-based alloy, a nickel-based alloy, a cobalt-based alloy, an iron-based alloy, a copper-based alloy or a molybdenum-based alloy.

10. The method of any of the preceding clauses, wherein the sintering additive comprises at least one of: magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron monoboride (FeB) iron boride (Fe ₂ B), silicon triboride (S1B3) silicon tetraboride (S1B4), boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaBe), silicon (Si), magnesium (Mg), yttrium oxide (Y2O3), silicon carbide (SiC), iron (Fe), and combinations thereof.

11. The method of any of the preceding clauses, wherein the final additively manufactured article comprises a sintering additive content of not greater than 5.0 wt. %.

12. The method of any of the preceding clauses, wherein the final additively manufactured article comprises a sintering additive content of from 0.03 wt. % to 5.0 wt. %.

13. The method of any of the preceding clauses, wherein the final additively manufactured article comprises a sintering additive content of from 0.05 wt. % to 3.5 wt. %.

14. The method of any of the preceding clauses, wherein the final additively manufactured article comprises a sintering additive content of from 0.1 wt. % to 1.0 wt. %.

15. A method comprising:

(a) heating a metal alloy to form a molten metal alloy;

(b) mixing a sintering additive and the molten metal alloy to form a molten metal alloy mixture;

(c) forming liquid droplets of the mixed molten metal alloy;

(d) cooling the liquid droplets to form a powder comprising the metal alloy and the sintering additive, wherein the powder has a D50 of not greater than 200 microns.

16. The method of clause 15, comprising:

(a) depositing a first layer of a powder comprising a metal alloy and a sintering additive onto a deposition surface;

(b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder; and

(c) repeating steps (a)-(b) to build an additively manufactured article,

wherein the sintering additive is configured to improve physical properties of a final additively manufactured article. 17. The method of clauses 15-16, wherein the sintering additive is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

18. The method of any of clauses 15-17, comprising: heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article.

19. The method of any of clauses 15-18, comprising: heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article.

20. The method of clause 18-19 wherein the heating comprises densifying the additively manufactured article, wherein the additively manufactured article comprises a first relative density and, wherein the final additively manufactured article comprises a second relative density, wherein the second relative density is greater than the first relative density.

21. The method of any of clauses 15-20, wherein the deposition surface comprises one of: a previously bound layer of the binder fluid and the powder or a build substrate of a binder jet 3D printing apparatus

22. The method of any of clauses 15-21, wherein the heating comprises forming melting metal alloy constituents.

23. The method of any of clauses 15-22, wherein the sintering additive comprises one of a powder and a wire.

24. The method of any of clauses 15-23, comprising melting the sintering additive, wherein the melting comprises forming a molten additive.

25. The method of clause 24 comprising mixing the molten additive with the molten metal alloy. 26. The method of any of clauses 25, comprising mixing the sintering additive and the molten metal alloy via induction stirring.

27. The method of any of clauses 25, comprising mixing the sintering additive and the molten metal alloy under vacuum.

28. The method of any of clauses 25, comprising forming the liquid droplets of the mixed molten metal alloy via atomization

29. The method of clause 28, wherein the atomization comprises forcing the molten metal through an orifice.

30. The method of any of clauses 15-29, wherein the metal alloy comprises one of a titanium-based alloy, a nickel-based alloy, an aluminum-based alloy, a cobalt-based alloy, a copper-based alloy, a molybdenum-based alloy, or an iron-based alloy.

31. The method of any of clauses 15-30, wherein the sintering additive comprises at least one of magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron monoboride (FeB), iron boride (FeiB). silicon triboride (S1B3) silicon tetraboride (S1B4),, boron (B), boric oxide (B2O3), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), yttrium oxide (Y2O3), silicon carbide (SiC), iron (Fe), or combinations thereof.

32. The method of any of clauses 15-31, wherein the molten metal alloy comprises a sintering additive content, wherein the additive content comprises not greater than 5.0 wt. %.

33. The method of any of clauses 15-32, wherein the molten metal alloy comprises a sintering additive content of 0.03 wt. % to 5.0 wt. %.

34. The method of any of clauses 15-33, wherein the molten metal alloy comprises a sintering additive content of 0.1 wt. % to 1.0 wt. %.

35. The method of any of clauses 15-34, wherein the cooled powder comprises a D50 of 1 micron to 200 microns. 36. The method of any of clauses 15-35, wherein the final additively manufactured article comprises a sintering additive content of not greater than 5.0 wt. %.

37. The method of any of clauses 15-36, wherein the final additively manufactured article comprises a sintering additive content of 0.03 wt. % to 5.0 wt. %.

38. The method of any of clauses 15-37, wherein the final additively manufactured article comprises a sintering additive content of 0.05 wt. % to 3.5 wt. %.

39. The method of any of clauses 15-38, wherein the final additively manufactured article comprises a sintering additive content of 0.1 wt. % to 1.0 wt. %.

40. A method comprising:

(a) mixing a sintering additive, an additive manufacturing feedstock powder, organic additives and a carrier fluid to form a first mixture;

(b) spraying the first mixture to form droplets, wherein each droplet comprises carrier fluid, organic additive, sintering additive, and additive manufacturing feedstock powder;

(c) heating the droplets to evaporate the carrier fluid from the droplets and form a powder mixture comprising sintering additive particles, additive manufacturing feedstock powder particles, and organic additive.

41. The method of clause 40, comprising:

(a) depositing a first layer of the powder mixture onto a surface;

(b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture; and

(c) repeating steps (a)-(b) to build an additively manufactured article.

42. The method of any of clauses 40-41, wherein the sintering additive is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article. 43. The method of any of clauses 40-42, comprising: heating the additively manufactured article to a first temperature for a sufficient time to remove the binder fluid from the additively manufactured article.

44. The method of clause 43, comprising: heating the additively manufactured article to a second temperature for a sufficient time, wherein the heating comprises forming a final additively manufactured article.

45. The method of any of clauses 40-44 comprising density ing the additively manufactured article, wherein the additively manufactured article comprises a first relative density and, wherein the final additively manufactured article comprises a second relative density, wherein the second relative density is greater than the first relative density.

46. The method of any of clauses 40-45, wherein the carrier fluid comprises at least one of: water and ethanol.

47. The method of any of clauses 40-46, wherein the organic additives comprise at least one of: polyvinylalcohol, polyethylene glycol, and paraffins.

48. The method of any of clauses 40-47, wherein the first mixture is a slurry comprising from 15 wt. % to 35 wt. % of carrier fluid and from 1.0 wt. % to 5.0 wt. % of organic additives.,

49. The method of any of clauses 40-48, wherein the mixture comprises a balance of sintering additive and additive manufacturing feedstock powder.

50. The method of any of clauses 40-49, wherein the sintering additive comprises at least one of boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron monoboride (FeB) iron boride (FeiB). silicon triboride (S1B3) silicon tetraboride (S1B4), boron (B), boric oxide (B2O3), lanthanum hexaboride (LaBe), silicon (Si), magnesium (Mg), yttrium oxide (Y2O3), silicon carbide (SiC), iron (Fe), and combinations thereof.

51. The method of any of clauses 40-50, wherein the D50 of the sintering additive comprises not greater than 20 microns. 52. The method of any of clauses 40-51, wherein the D50 of the sintering additive comprises from 0.05 microns to 5 microns.

53. The method of any of clauses 40-52, wherein the additive manufacturing feedstock powder comprises at least one of: a metal, a metal alloy, a metal oxide, a non-oxide, a boride, a carbide, a nitride, and combinations thereof.

54. The method of any of clauses 40-53, wherein the powder mixture has an average size of not greater than 200 microns.

55. The method of any of clauses 40-54, wherein the D50 of the powder mixture comprises from 1 micron to 200 microns.

56. The method of any of clauses 40-55, wherein the final additively manufactured article comprises a sintering additive content of not greater than 5.0 wt. %.

57. The method of any of clauses 40-56, wherein the final additively manufactured article comprises a sintering additive content of 0.03 wt. % to 5.0 wt. %.

58. The method of any of clauses 40-57, wherein the final additively manufactured article comprises a sintering additive content of 0.05 wt. % to 3.5 wt. %.

59. The method of any of clauses 40-58, wherein the final additively manufactured article comprises a sintering additive content of 0.1 wt. % to 1.0 wt. %.

60. A method comprising:

(a) depositing a first layer of an additive coated powder onto a deposition surface, wherein the additive coated powder comprises an additive manufacturing feedstock powder, wherein the additive manufacturing feedstock comprises a coating, wherein the coating comprises a sintering additive;

(b) depositing a binder fluid onto the first layer to form a first bound layer comprising the binder fluid and the additive coated powder; and;

(c) repeating steps (a)-(b) to build an additively manufactured article. 61. The method of clause 60, wherein the sintering additive is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

62. The method of any of clauses 60-61, wherein, the deposition surface is one of: a previously bound layer of binder fluid and additive coated powder or a build substrate of a binder jet 3D printing apparatus.

63. The method of clause 60-62, comprising: heating the additively manufactured article to a first temperature for a sufficient time to remove the binder from the additively manufactured article.

64. The method of any of clauses 60-63, comprising: heating the additively manufactured article to a second temperature for a sufficient time to form the final additively manufactured article.

65. The method of any of clauses 60-64 comprising density ing the additively manufactured article, wherein the additively manufactured article comprises a first relative density and, wherein the final additively manufactured article comprises a second relative density, wherein the second relative density is greater than the first relative.

66. The method of any of clauses 60-65, wherein the additive manufacturing feedstock powder particles comprise a coating, wherein the coating comprises a sintering additive.

67. The method of clause 66 wherein the coating comprises covering the entire surface of the particle.

68. The method of clause 66 wherein the coating comprises partially covering the surface of the particle.

69. The method of any of clauses 60-68, wherein the additive manufacturing feedstock powder comprises at least one of a metal, a metal alloy, a metal oxide, a non-oxide, a boride, a carbide, a nitride, and combinations thereof. 70. The method of any of clauses 60-69, wherein the additive manufacturing feedstock powder comprises one of: a titanium-based alloy, an aluminum-based alloy, a nickel-based alloy, a cobalt-based alloy, an iron-based alloy, a copper-based alloy or a molybdenum-based alloy.

71. The method of any of clauses 60-70, wherein the sintering additive comprises at least one of: magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron monoboride (FeB) iron boride (Fe ₂ B), silicon triboride (S1B3) silicon tetraboride (S1B4),, boron (B), boric oxide (B ₂ 03), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), ytrium oxide (Y ₂ 03), silicon carbide (SiC), iron (Fe), and combinations thereof.

72. The method of any of clauses 60-71, wherein the coating comprises chemically reacting the additive manufacturing feedstock powder with the sintering additive.

73. The method of any of clauses 60-72, wherein the coating comprises depositing the sintering additive onto the additive manufacturing feedstock powder via a chemical vapor deposition process or a physical vapor deposition process.

74. The method of any of clauses 60-73, wherein the final additively manufactured article comprises a sintering additive content of not greater than 5.0 wt. %.

75. The method of any of clauses 60-74, wherein the final additively manufactured article comprises a sintering additive content of 0.03 to 5.0 wt. %.

76. The method of any of clauses 60-75 wherein the final additively manufactured article comprises a sintering additive content of 0.05 wt. % to 3.5 wt. %.

77. The method of any of clauses 60-76, wherein the final additively manufactured article comprises a sintering additive content of 0.1 to 1.0 wt. %.

78. An apparatus comprising:

(a) a first material storage unit configured to (i) store an additive manufacturing feedstock powder and (ii) deposit the additive manufacturing feedstock powder; (b) a second material storage unit configured to (i) store a sintering additive and (ii) deposit the sintering additive;

(c) a deposition surface configured to receive the additive manufacturing feedstock powder from the first material storage unit and configured to receive the sintering additive from the second material storage unit; and

(d) a binder fluid dispenser configured to (i) deposit a binder fluid onto at least one of: (a) the deposition surface, (b) a deposited additive manufacturing feedstock powder, and (c) a deposited sintering additive.

79. The apparatus of clause 78, wherein the deposition surface is a build platform of a binder jet 3D printing apparatus.

80. The apparatus of any of clauses 78-79, wherein the deposition surface is a prior layer of the additive manufacturing feedstock powder and the sintering additive.

81. The apparatus of any of clauses 78-80, wherein the additive manufacturing feedstock powder comprises at least one of a metal, a metal alloy, a metal oxide, a non-oxide, a boride, a carbide, a nitride, and combinations thereof.

82. The apparatus of any of clauses 78-81, wherein the additive manufacturing feedstock powder comprises one of: a titanium-based alloy, an aluminum-based alloy, a nickel-based alloy, a cobalt-based alloy, an iron-based alloy, a copper-based alloy or a molybdenum-based alloy.

83. The apparatus of any of clauses 78-82, wherein the sintering additive comprises at least one of: magnesium (Mg), boron nitride (BN), magnesium diboride (MgB ₂ ), aluminum diboride (AIB2), nickel boride (NiB), iron monoboride (FeB) iron boride (FeiB). silicon triboride (S1B3) silicon tetraboride (S1B4), boron (B), boric oxide (B2O3), lanthanum hexaboride (LaB ₆ ), silicon (Si), magnesium (Mg), yttrium oxide (Y2O3), silicon carbide (SiC), iron (Fe), and combinations thereof.

84. A method comprising: (a) depositing a first layer of a powder mixture on to a deposition surface, wherein the powder mixture comprises an additive manufacturing feedstock powder and a boron containing material;

(b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture;

(c) repeating steps (a)-(b) to build an additively manufactured article.

85. The method of clause 84, wherein the boron containing material is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

86. A method comprising:

(a) heating a metal alloy to form a molten metal alloy;

(b) mixing a boron containing powder and the molten metal alloy to form a molten metal alloy mixture;

(c) forming liquid droplets of the molten metal alloy mixture;

(d) cooling the liquid droplets to form a powder comprising the metal alloy and the additive, wherein the powder has a Dso of not greater than 200 microns.

87. The method of clause 86, comprising:

(a) depositing a first layer of the powder onto a deposition surface;

(b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder;

(c) repeating steps (a)-(b) to build an additively manufactured article.

88. The method of any of clauses 86-87, wherein the boron containing powder is

configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

89. A method comprising:

(a) mixing a boron containing powder, an additive manufacturing feedstock powder, organic additives and a carrier fluid to form a first mixture;

(b) spraying the first mixture to form droplets, wherein each droplet comprises carrier fluid, organic additive, boron containing powder, and additive manufacturing feedstock powder;

(c) heating the droplets to evaporate the carrier fluid from the droplets and form a powder mixture comprising boron containing powder particles, additive

manufacturing feedstock powder particles, and organic additive.

90. The method of clause 89, comprising:

(a) depositing a first layer of the powder mixture onto a deposition surface;

(b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and powder mixture, and;

(c) repeating steps (a)-(b) to build an additively manufactured article,

91. The method of any of clauses 89-90, wherein the boron containing powder is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

92. A method comprising:

(a) depositing a first layer of an additive manufacturing feedstock powder mixture onto a surface, wherein the additive manufacturing feedstock powder mixture comprises additive manufacturing feedstock powder coated with boron containing powder to form an additive coated powder; (b) depositing a binder fluid onto the first layer to form a first bound layer of binder fluid and additive coated powder; and

(c) repeating steps (a)-(b) to build an additively manufactured article,

wherein, the surface comprises a previously bound layer of binder fluid and additive coated powder or a build substrate of a binder jet 3D printing apparatus.

93. A method comprising:

(a) depositing a layer of an additive manufacturing feedstock powder onto a surface;

(b) depositing a mixture onto the layer of additive manufacturing feedstock powder, wherein the mixture comprises a sintering additive and a binder fluid, wherein the mixture comprises from 0.03 vol. % to 41 vol. % of the sintering additive, wherein the depositing step comprises forming a first bound layer comprising binder fluid, sintering additive, and additive manufacturing feedstock powder;

(c) repeating steps (a)-(b) to build an additively manufactured article,

94. The method of clause 93, wherein the mixture is configured to at least one of: improve densification of a final additively manufactured article, lower porosity of a final additively manufactured article, lower impurities of a final additively manufactured article, and improve homogeneity of a final additively manufactured article.

95. The method of any of clauses 93-94, wherein the final additively manufactured article has a sintering additive content of from 0.1 wt. % to 5.0 wt. %.

96. The method of any of clauses 93-95, wherein the final additively manufactured article has a sintering additive content of from 0.05 wt. % to 3.5 wt. %.

97. The method of any of clauses 93-96, wherein the sintering additive is Mg and the mixture comprises 0.13 vol. % to 41 vol. % Mg.

98. The method of any of clauses 93-97, wherein the sintering additive is Mg and the mixture comprises 0.06 vol. % to 32 vol. % Mg. 99. The method of any of clauses 93-98, wherein the sintering additive is BN and the mixture comprises 0.10 vol. % to 35 vol. %.

100. The method of any of clauses 93-99, wherein the sintering additive is BN and the mixture comprises 0.05 vol. % to 27 vol. % BN and the balance is binder fluid.

101. The method of any of clauses 93-100, wherein the sintering additive is Si and the mixture comprises 0.09 vol. % to vol. 34 % Si.

102. The method of any of clauses 93-101, wherein the sintering additive is Si and the mixture comprises 0.05 vol. % to vol. 26% Si.

103. The method of any of clauses 93-102, wherein the sintering additive is B and the mixture comprises 0.09 vol. % to 34 vol. % B.

104. The method of any of clauses 93-103, wherein the sintering additive is B and the mixture comprises 0.05 vol. % to 26 vol. % B.

105. The method of any of clauses 93-104, wherein the sintering additive is SiB3 and the mixture comprises 0.09 vol. % to 33 vol. % SiB ₃ .

106. The method of any of clauses 93-105, wherein the sintering additive is SiB3 and the mixture comprises 0.04 vol. % to 25 vol. % SiB ₃ .

107. The method of any of clauses 93-106, wherein the sintering additive is MgB ₂ and the mixture comprises 0.09 vol. % to 32 vol. %.

108. The method of any of clauses 93-107, wherein the sintering additive is MgB ₂ and the mixture comprises 0.04 vol. % to 25 vol. % MgB ₂ .

109. The method of any of clauses 93-108, wherein the sintering additive is B ₂ C and the mixture comprises 0.07 vol. % to 28 vol. % B ₂ 03.

110. The method of any of clauses 93-109, wherein the sintering additive is B ₂ C and the mixture comprises 0.04 vol. % to 21 vol. % B ₂ 0 ₃ .

111. The method of any of clauses 93-110, wherein the sintering additive is AlB ₂ and the mixture comprises 0.07 vol. % to 28 vol. % AlB ₂ . 112. The method of any of clauses 93-111, wherein the sintering additive is AIB2 and the mixture comprises 0.03 vol. % to 21 vol. % A1B2.

113. The method of any of clauses 93-112, wherein the sintering additive is SiC and the mixture comprises 0.11 vol. % to 27 vol. % SiC.

114. The method of any of clauses 93-113, wherein the sintering additive is SiC and the mixture comprises 0.03 vol. % to 21 vol. % SiC.

115. The method of any of clauses 93-114, wherein the sintering additive is LaBr, and the mixture comprises 0.05 vol. % to 20 vol. % LaB6.

116. The method of any of clauses 93-115, wherein the sintering additive is LaBr, and the mixture comprises 0.02 vol. % to 21 vol. % LaB6.

117. The method of any of clauses 93-116, wherein the sintering additive is Y2O3 and the mixture comprises 0.04 vol. % to 19 vol. % Y2O3.

118. The method of any of clauses 93-117, wherein the sintering additive is Y2O3 and the mixture comprises 0.02 vol. % to 14 vol. % Y2O3.

119. The method of any of clauses 93-118, wherein the sintering additive is FeB and the mixture comprises 0.03 vol. % to 14. vol. % FeB.

120. The method of any of clauses 93-119, wherein the sintering additive is FeB and the mixture comprises 0.02 vol. % to 10 vol. % FeB.

121. The method of any of clauses 93-120, wherein the sintering additive is NiB and the mixture comprises 0.03 vol. % to 14 vol. % NiB.

122. The method of any of clauses 93-121, wherein the sintering additive is NiB and the mixture comprises 0.02 vol. % to 10 vol. % NiB.

123. The method of any of clauses 93-122, wherein the sintering additive is Fe and the mixture comprises 0.03 vol. % to 13 vol. % Fe.

124. The method of any of clauses 93-123, wherein the sintering additive is Fe and the mixture comprises 0.01 vol. % to 10 vol. % Fe.