Cross-Reference to Related Application

[0001] The present application claims priority to U.S. Provisional Patent Application No. 61/702,007, entitled "Bulk Nickel-Silicon-Boron Glasses Bearing Chromium", filed on September 17, 2012, and U.S. Provisional Patent Application No. 61/847,961 , entitled "Bulk Nickel-Silicon-Boron Glasses Bearing Chromium and Molybdenum", filed on July 18, 2013, both of which are incorporated herein by reference in their entirety.

Technical Field

[0002] The present disclosure generally relates to nickel-silicon-boron (Ni-Si-B) alloys capable of forming bulk metallic glasses. More specifically, the disclosure relates to adding chromium (Cr) and/or phosphorus (P) or molybdenum (Mo) to the Ni-Si-B alloy to improve metallic glass-forming ability (GFA).

Background

[0003] Nickel alloys have been reported that form metallic glasses with diameters below 200 micrometers. For example, Japanese patent JP-08-269647 (1996), entitled "Ni-Based

Amorphous Metallic Filament", by Takeshi Masumoto, et al., discloses Ni ₁₀₀ ^ _c Si _fa B _c alloys, where subscripts b and c denote atomic percents for Si and B, respectively, 3 < b < 17, and 10 < c < 27, that can form amorphous wires with diameters on the order of tens of micrometers via a spinning method in a rotating liquid. The Masumoto et al. reference lists a variety of possible additions, including Fe, Co, Nb, Ta, Mo, V, W, Cr, Mn, Cu, P, C, and germanium, that can be included to improve the tensile strength, heat resistance, and corrosion resistance of the alloys. Although the Masumoto et al., reference does not specifically teach certain ranges for Cr additions, they do disclose that Fe, Co, Nb, Ta, Mo, V, W, Mn, Cu, P, C, Ge as well as Cr could be added to improve the tensile strength, the heat resistance and corrosion resistance of the alloys. The Ni-Si-B alloy of Masumoto contained 13% Cr and is reported to have a casting diameter of only 50 micrometers.

Further, the Ni-Si-B alloys or Ni-Cr-Si-B alloys described in the Masumoto et al. reference are generally limited to diameters below 200 micrometers, and the authors describe that "crystalline phases emerge and the processability [of the alloys] worsens when the wires exceed 200 micrometers [in diameter]."

[0004] It is thus desirable to develop nickel bulk metallic glasses with greater thicknesses and methods of making the same. Summary

[0005] Embodiments described herein provide Ni-Cr-Si-B, Ni-Cr-S-B-P or Ni-Cr-Mo-Si-B-P alloys that are capable of forming metallic glass rods with diameters of at least 1 mm.

Embodiments described herein are further directed to a metallic glass comprising such alloy compositions. The chromium containing alloys Ni-Cr-Si-B or Ni-Cr-Si-B-P have better glass forming ability than Ni-Si-B alloys that do not contain chromium. The phosphorous containing Ni-Cr-Si-B-P alloys have even better glass forming ability than the Ni-Cr-Si-B alloys that do not contain phosphorous. The molybdenum containing Ni-Cr-Mo-Si-B-P alloys have better glass forming ability and higher notch toughness than the Ni-Cr-Si-B-P alloys. Additionally, the metallic glass rods with diameters up to 1 mm can be plastically bent.

Embodiments also provide a fluxing method to further improve glass-forming ability for the Ni-Cr-Si-B alloys, the Ni-Cr-Si-B-P alloys, and the Ni-Cr-Mo-Si-B-P alloys.

[0006] In one embodiment, an alloy capable of forming a bulk metallic glass is provided. The alloy or the metallic glass has the composition Ni _{(1 0} o-a-t>-c) Cr _a Si _fa B _c , where an atomic percent of chromium (Cr) a is between 3 and 8, an atomic percent of silicon (Si) b is between 10 and 14, an atomic percent of boron (B) c is between 9 and 13, and the balance is Ni, and wherein the alloy is capable of forming a metallic glass rod having a diameter of at least 1 mm.

[0007] In another embodiment, an alloy capable of forming bulk metallic glass is provided. The alloy or the metallic glass has the composition Ni( ₁ oo-a- _t >-c-d ₎ Cr _a Si _fa B _c P _c , where an atomic percent of chromium (Cr) a is between 3 and 8, an atomic percent of silicon (Si) b is between 4 and 12, an atomic percent of boron (B) c is between 9 and 13, an atomic percent of phosphorus (P) d \s between 0.5 and 8, and the balance is Ni, and wherein the alloy is capable of forming metallic glass rod having a diameter of at least 1 mm.

[0008] The disclosure is also directed to an alloy or metallic glass having a composition selected from the group consisting of , Ni ₇₁ .5Cr5. ₅ Si ₆ B _{1 2} P5,

Ni72Cr5.5Si5.75Bn .75P5. N i72Cr _{5 5} Si6B _{1 1} .5P5, i71.75Cr5.75Si5.75Bn .75P5, Ni72Cr5.5Si5.5Bn .75P5.25, and Ni72.25Cr525Si5.75B11 75P5.

[0009] In another embodiment, Ni-Cr-Mo-Si-B-P alloys are disclosed capable of forming a metallic glass rod having a diameter of at least or greater than 2 mm, or alternatively at least 3 mm when processed by melt water quenching in fused silica tubes having wall thickness of 0.5 mm.

[0010] The disclosure is directed to an alloy capable of forming a bulk metallic glass, the alloy is represented by the following formula (subscripts denote atomic percent):

where a is between 3.5 and 6, b is up to 2, c is between 4.5 and 7, d is between 10.5 and 13, and e is between 4 and 6. [0011] In another embodiment, c + d + e in Eq. 1 is between 21 .5 and 23.5.

[0012] In another embodiment, a + b in Eq. 1 is between 4.5 and 6.5 while b is between

0.25 and 1 .5.

[0013] In another embodiment, a + b in Eq. 1 is between 5 and 6 while b is between 0.5 and 1 .25, and wherein the metallic glass rod diameter when processed by water quenching the high temperature melt in a fused silica tube having wall thickness of 0.5 mm is at least 2.5 mm.

[0014] In yet another embodiment, up to 2 atomic percent of Ni is substituted by Fe, Co, W, Mn, Ru, Re, Cu, Pd, Pt, or combinations thereof.

[0015] In yet another embodiment, the melt is fluxed with a reducing agent prior to rapid quenching.

[0016] In yet another embodiment, the melt temperature prior to quenching is at least 200 °C above the liquidus temperature of the alloy.

[0017] In yet another embodiment, the melt temperature prior to quenching is at least 1200°C.

[0018] In yet another embodiment, the compressive yield strength is at least 2600 MPa.

[0019] In yet another embodiment, a wire made of such glass having a diameter of 1 mm can undergo macroscopic plastic deformation under bending load without fracturing catastrophically.

[0020] The disclosure is also directed to an alloy capable of forming a metallic glass having a composition selected from the group consisting of Ni72Cr5Moo.5Si5.75B .75P5,

Ni72Cr4.75Moo.75Si5.75B11 75P5, Ni ₇₂ Cr ₄ . ₅ Mo ₁ S15.75B11 75P5, Ni ₇₂ Cr ₄ .2 ₅ Mo ₁ .25815.75611 75P5, and Ni72Cr4M01.5Si5.75Bn .75P5-

[0021] In another embodiment, the disclosure is also directed to a metallic glass

represented by formula Ni ₍ i oo-a-t>-c- _C i- _e) Cr _a Mot ₎ Si _c B _c P _e; wherein subscripts a, b, c, d, and e denote atomic percents for Cr, Mo, Si, B and P, a is between 3.5 and 6, b is up to 2, c is between 4.5 and 7, d \s between 10.5 and 13, e is between 4 and 6, and the balance is Ni. In some embodiments, the metallic glass rod diameter that can form when processed by water quenching the high temperature melt in a fused silica tube having wall thickness of 0.5 mm is at least 2 mm. In some embodiments, the stress intensity at crack initiation of the metallic glass when measured on a 2 mm diameter metallic glass rod containing a notch with length between 0.75 and 1 .25 mm and root radius between 0.1 and 0.15 mm is at least 55 MPa m ^{1 2} .

[0022] In another embodiment, the disclosure is also directed to a metallic glass having a composition selected from the group consisting of Ni72Cr5Moo.5Si5.75Bn .75P5,

Ni72Cr4.75Moo.75Si5.75B11 75P5, Ni ₇₂ Cr ₄ . ₅ Moi S15.75B11 75P5, Ni ₇₂ Cr ₄ .2 ₅ Moi .25815.75611 75P5, and Ni72Cr4M01.5Si5.75Bn .75P5- [0023] In a further embodiment, a method is provided for forming a bulk metallic glass. The method includes melting an alloy described herein into a molten state, and quenching the molten alloy at a cooling rate sufficiently rapid to prevent crystallization of the alloy. The method also can include a step of fluxing of the molten alloy prior to quenching using a reducing agent to improve the glass-forming ability.

[0024] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.

Brief Description of the Drawings

[0025] FIG. 1 provides a data plot showing the effect of substituting Ni by Cr on the glass- forming ability of Ni-Cr-Si-B alloys according to embodiments of the present disclosure.

[0026] FIG. 2 provides calorimetry scans for sample Ni-Cr-Si-B metallic glasses with varying Cr atomic concentrations shown in Table 1 according to embodiments of the present disclosure.

[0027] FIG. 3 provides a data plot showing the effect of substituting Si by P on the glass- forming ability of the Ni-Cr-Si-B-P alloy according to embodiments of the present disclosure.

[0028] FIG. 4 provides a data plot showing the effect of substituting Ni by Cr on the glass- forming ability of sample Ni-Cr-Si-B and Ni-Cr-Si-B-P alloys according to embodiments of the present disclosure.

[0029] FIG. 5 provides calorimetry scans for sample Ni-Cr-Si-B-P metallic glasses with varying P atomic concentrations shown in Table 2 according to embodiments of the present disclosure.

[0030] FIG. 6 provides data plots showing the effect of varying the metalloid atomic concentration with the metal atomic concentration on the glass-forming ability of sample Ni- Cr-Si-B-P alloys.

[0031] FIG. 7 provides calorimetry scans for sample Ni-Cr-Si-B-P metallic glasses with varying metalloid atomic concentrations shown in Table 2 according to embodiments of the present disclosure.

[0032] FIG. 8 provides an optical image of a 2.5 mm metallic glass rod having composition Ni72Cr5.5Si5.75B .75P5 according to embodiments of the present disclosure.

[0033] FIG. 9 provides an X-ray diffractogram verifying the amorphous structure of a 2.5 mm metallic glass rod having composition Ni72Cr5.5Si5.75Bn .75P5 according to embodiments of the present disclosure [0034] FIG. 10 provides a differential calorimetry scan of sample metallic glass

Ni72Cr5.5Si5.75B11.75Γ5.

[0035] FIG. 1 1 provides an optical image of a plastically bent 1 mm metallic glass rod having composition Ni72Cr5.5Si6B .75P4.75 according to embodiments of the present disclosure.

[0036] FIG. 12 provides a plot showing the effect of substituting Cr by Mo on the glass forming ability of alloys having compositions Ni72Cr5.5-JvlOxSi5.75Bn .75P5- [0037] FIG. 13 provides a plot showing calorimetry scans having a scan rate of 20 K/min for sample metallic glasses Ni72Cr5.5-JvlOxSi5.75B11.75 5- Arrows from left to right designate the glass-transition and liquidus temperatures, respectively.

[0038] FIG. 14 provides an optical image of a 3 mm metallic glass having composition Ni72Cr4.5M01 Si5.75Bn .75P5-

[0039] FIG. 15 provides an X-ray diffractogram verifying the amorphous structure of a 3 mm metallic glass rod having composition Ni72Cr4.5M01 Si5.75Bn .75P5- [0040] FIG. 16 provides a plot showing the effect of substituting Cr by Mo on the notch toughness of sample metallic glass having composition Ni72Cr5.5-xMOxSi5.75Bn .75P5-

[0041] FIG. 17 provides compressive stress-strain diagrams for sample metallic glass having composition Ni72Cr5.5-xMOxSi5.75Bn .75P5-

[0042] FIG. 18 provides an optical image of a plastically bent 1 mm metallic glass rod having composition Ni7 ₂ Cr ₄ .5Moi Si5.75Bn .75P5- [0043] FIG. 19 provides a plot showing the corrosion depth versus time in 6M HCI solution of a 2 mm metallic glass rod having composition Ni72Cr4.5M01 Si5.75Bn .75P5- [0044] Reference is now made to certain embodiments. The disclosed embodiments are not intended to be limiting of any claim supported by this disclosure. To the contrary, the appended claims are intended to cover all alternatives, modifications, and equivalents.

Detailed Description

[0045] The present disclosure may be understood by reference to the following detailed description, taken in conjunction with the drawings as described below. It is noted that, for purposes of illustrative clarity, certain elements in various drawings may not be drawn to scale.

[0046] The present disclosure provides Ni-Cr-Si-B, Ni-Cr-Si-B-P, and Ni-Cr-Mo-Si-B-P alloys capable of forming bulk metallic glasses. By controlling the relative concentrations of Ni, Si, and B, and by incorporating minority additions of Cr to substitute Ni, the alloy has better glass forming ability than Ni-Si-B alloys. By incorporating P to substitute Si in the Ni-Cr-Si-B alloys, the alloys are capable of forming a metallic glass rods having diameters of at least 1 mm, and up to 2.5 mm or greater. By incorporating Mo to substitute Cr in the Ni-Cr-Si- B-P, the alloys are capable of forming metallic glass rods having diameters of up to 3 mm or greater.

[0047] As described in the "Background", alloys incorporating a combination of Ni-Cr-Si-B have been disclosed in the past, but they have not shown bulk processability. In general, the glass-forming ability of each alloy may be assessed by determining the maximum or "critical" rod diameter in which the amorphous phase can be formed when processed by a method of water quenching a molten alloy described herein. Water quenching of the molten alloy may be performed in quartz capillaries or tubes. Since quartz is known to be a poor heat conductor that retards heat transfer, the quartz thickness is a critical parameter associated with the glass-forming ability of the sample alloys. Therefore, to quantify the glass-forming ability of each of the sample alloys, the critical rod diameter, d _c , is reported in conjunction with the associated quartz thickness, t _w , of the capillary or tube used to process the alloy.

[0048] In the present disclosure, it has been discovered that the addition of Cr in a very specific range promotes bulk-glass formation in Ni-Si-B alloys. In particular, the present alloys include Cr between 1 % and 10% (atomic percent), with a peak around 5.5 %. This low Cr content runs contrary to Masumoto (JP-08-269647). Masumoto allows, and provides an example of, Cr exceeding 10 %.

[0049] It has also been discovered that glass formation may be further promoted by the addition of phosphorus (P) to the Ni-Cr-Si-B alloy, a possibility not disclosed by Masumoto. In particular, Ni-Cr-Si-B-P alloys that include P in the range of 1 % to 8 % may have better glass-forming ability than P-free Ni-Cr-Si-B alloys.

[0050] It has further been discovered that when up to 2 atomic percent Mo is added to Ni- Cr-Si-B-P alloys to substitute Cr, the glass forming ability of the alloys is further enhanced. In such instances, the alloy is capable of forming metallic glass rods having diameters of up to 3 mm or greater. In addition, such alloys can have a notch toughness that increases from under 50 MPa m ^{1 2} for the Mo-free metallic glasses to at least 65 MPa m ^{1 2} for the Mo- bearing metallic glasses. In an example of the present disclosure, the Ni-Cr-Mo-Si-B-P composition includes (in atomic percent) about 4.5 to 5 % Cr, about 0.5 to 1 % Mo, about 5.75 % Si, about 1 1 .75 % B, about 5 atomic percent of P, and the balance is Ni. [0051] Furthermore, the present disclosure provides a fluxing process to improve glass- forming ability even further. Fluxing is a chemical process by which the fluxing agent acts to "reduce" the oxides entrained in the glass-forming alloy that could potentially impair glass formation by catalyzing crystallization. The benefits of fluxing in promoting glass formation are determined by the chemistry of the alloy, the entrained oxide inclusions, and the fluxing agent. It has now been discovered that for the Ni-Si-B alloys claimed in the instant disclosure, fluxing with boron oxide (B ₂ 0 ₃ ) dramatically improves bulk-glass formation. Ni-Cr-Si-B Alloys and Metallic Glasses

[0052] In one aspect, the alloy or metallic glass (i.e. alloy in amorphous form) is represented by the following formula:

Ni ₍ ioo-a-t>-c ₎ Cr _a Si _t ,B _c (2) where subscripts a, b, and c denote atomic percents for Cr, Si, and B, respectively. An atomic percent of Cr is between 3 and 8, an atomic percent of Si is between 10 and 14, an atomic percent of B is between 9 and 13, and the balance is Ni. The alloy is capable of forming a metallic glass rod having a diameter of at least 1 mm. In a particular embodiment, a combined atomic percent of Si and B is between 21 and 24. In another particular embodiment, an atomic percent of Cr is between 4.5 and 6.5. In a further particular embodiment, up to 2 atomic percent of Cr is substituted by Fe, Co, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, Nb, V, Ta, or combinations thereof. In yet another particular embodiment, up to 2 atomic percent of Ni is substituted by Fe, Co, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, Nb, V, Ta, or combinations thereof. In yet another particular embodiment, the alloy or the metallic glass has composition .

[0053] Sample alloys that satisfy the disclosed formula shown in Eq. (2) are presented in Table 1 . In the sample metallic glasses described in Table 1 , the Si content is 12 atomic percent and the B content is 1 1 atomic percent for samples 1 -9, while in sample metallic glasses 1 -9 the Cr and Ni contents are varied. For some samples, such as 3, 5, 7, and 9, the critical rod diameter of metallic glasses produced with or without the fluxing is presented. For the remaining samples, such as Samples 1 -2, 4, 6, and 8, only the critical rod diameter of the metallic glasses produced with fluxing is presented.

Table 1 . Sample metallic glasses Ni-Cr-Si-B

and glass-forming ability of alloys

9 NieeCrgSii ₂ B ₁₁ Fluxed 0.7 0.07

Unfluxed 0.7 0.07

[0054] At a first stage of experiments, quartz capillaries with wall thicknesses that were about 10% of the tube inner diameter were used for processing the alloys to form the sample metallic glasses. A ternary eutectic in the ternary Ni-Si-B alloy was identified at composition

. When fluxed with B ₂ 0 ₃ and processed in a capillary with a 0.05 mm thick wall, the ternary alloy was found capable of forming 0.5 mm diameter metallic glass rods.

[0055] FIG. 1 provides a data plot of the critical rod diameter for samples 1 -9 in Table 1 showing the effect of substituting Ni by Cr on the glass-forming ability of Ni-Cr-Si-B alloys according to the formula . As shown in FIG. 1 , substituting Ni by Cr in the range between 3 % and 8 % was found to significantly improve metallic glass formation over the alloy without any Cr, as metallic glass rods of 1 mm or larger can be produced when fluxed with B ₂ 0 ₃ . The alloy having composition (sample 5) corresponding to 5.5% Cr substitution exhibits the highest glass forming ability, being able to form metallic glass rods of nearly 2 mm when the quartz capillary wall thickness is about 0.2 mm .

[0056] Without any Cr, the rod diameter is about 0.5 mm when fluxed, much smaller than the 2 mm with 5.5 % Cr. With the Cr content increasing from 5.5 to 9 atomic percent, the glass-forming ability is reduced to the levels of the Cr-free alloy. As shown, the Ni-Cr-Si-B alloy was found to reveal bulk glass-forming ability within a limited range of Cr.

[0057] As shown in FIG. 1 , the alloys having the same composition but being fluxed

(represented by solid circles) were found to have better glass-forming ability than the unfluxed (represented by open squares) over the range of Cr between 1 and 10 atomic percent. For example, the alloy has a critical rod diameter of about 2 mm when fluxed, but only about 0.8 mm if unfluxed. Outside that range the effect of fluxing on improving glass forming ability diminishes. As shown in FIG. 1 , the alloy with 9 % of Cr has a critical rod diameter of about 0.7 mm whether fluxed or unfluxed.

[0058] FIG. 2 provides calorimetry scans for Ni-Cr-Si-B metallic glasses having varying Cr atomic concentrations shown in Table 1 according to embodiments of the present disclosure. The arrows designate the liquidus temperatures of the alloys. From the calorimetry scans, it is evident that the Ni-Cr-Si-B alloys have lower liquidus temperatures as compared to those of the ternary Ni-Si-B alloys, with a minimum liquidus temperature occurring around the Cr addition of 5.5 %. Lower liquidus temperatures are desirable, as it implies an improved potential for glass formation.

Ni-Cr-Si-B-P Alloys and Metallic Glasses [0059] In another aspect, the alloy or metallic glass (i.e. the alloy in the amorphous phase) is represented by the following formula:

ifio _O - _a - _b - _c - _c Cr _a Si _b B _c P _d (3) where subscripts a, b, c and d denote atomic percents for Cr, Si, B, and P, respectively, an atomic percent of chromium (Cr) a is between 3 and 8, an atomic percent of silicon (Si) b is between 4 and 12, an atomic percent of boron (B) c is between 9 and 13, an atomic percent of phosphorus (P) c is between 0.5 and 8, and the balance is Ni.

[0060] In a particular embodiment, a combined atomic percent of Si, B and P, i.e. b, c, and d is between 21 and 24. In another particular embodiment, the atomic percent of Cr is between 4.5 and 6.5. In a further particular embodiment, up to 2 atomic percent of Cr is substituted by iron (Fe), Cobalt (Co), Manganese (Mn), Tungsten (W), Molybdenum (Mo), Ruthenium (Ru), Rhenium (Re), Copper (Cu), Palladium (Pd), Platinum (Pt), Niobium (Nb), Vanadium (V), Tantalum (Ta), or combinations thereof. In yet another particular embodiment, up to 2 atomic percent of Ni is substituted by Fe, Co, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, Nb, V, Ta, or combinations thereof. In yet another embodiment, the metallic glasses or alloy compositions include Ni ₇₁ .5Cr5.5Si ₆ B ₁₂ P5, Ni72Cr5.5Si5.75Bn .75P5, Ni72Cr5.5Si6Bn .5P5, Ni71.75Cr575Si5.75Bn 75P5 Ni ₇₂ Cr ₅ 5Si5.5Bi i 75P5.25, and Ni72.25Cr525Si5.75Bn 75P5.

[0061] Sample alloys or metallic glasses with compositions satisfying Eq. (3) are presented in Table 2. The atomic percent of Cr varies between 5% and 6% for samples 10-34, which is around the content of 5.5% that reveals the highest glass-forming ability among all the alloys investigated. The atomic percent of B also varies between 1 1 % and 12.5%. The atomic percent of P also varies between 4% and 6%. The combined atomic percent of Si, B, and P remains a constant of 23% for samples 10-19, but varies between approximately 21 % and 24% for samples 20-34.

[0062] The quartz tubes have relatively thicker wall thickness compared to those in Table 1 , ranging from about 0.2 mm to 0.5 mm. The Ni-Cr-Si-B-P alloys in Table 2 have better glass forming ability than the Ni-Cr-Si-B shown in Table 1 , as bulk metallic glass rods are being produced in quartz tubes with thicker walls.

Table 2. Sample metallic glasses Ni-Cr-Si-B-P

and glass-forming ability of alloys

15 Ni ₇₁ Cr ₆ Si ₇ B ₁₂ P ₄ Fluxed 2.8 0.28

16 Ni71 Cr6Si6.5B12.5P4 Fluxed 2.9 0.29

17 Ni ₇ i Cr ₆ Si ₆ Bi3P4 Fluxed 2.8 0.28

18 Ni ₇ i Cr ₆ Si ₅ Bi4P4 Fluxed 1 .6 0.16

19 Ni ₇₃ Cr ₆ Si ₆ Bi i P ₄ Fluxed 1 .7 0.17

20 Ni ₇₂ Cr ₆ Si ₆ . ₅ Bi 1 5P4 Fluxed 2.8 0.28

21 I71 5Cr6Si6.75Bl 1 75P4 Fluxed 3.1 0.31

22 Ni70Cr6Si7.5B12.5P4 Fluxed 2.0 0.2

23 Ni ₇₂ Cr ₅ Si ₇ Bi ₂ P ₄ Fluxed 2.9 0.29

24 N171 5Cr55S17B12P4 Fluxed 3.4 0.34

25 Ni7oCr ₇ Si ₇ Bi ₂ P ₄ Fluxed 2.8 0.28

26 Ni72Cr55Si5.25B12.25P5 Fluxed 3.0 0.30

27 Ni ₇₂ Cr _{5 5} Si ₅ 5B12P5 Fluxed 2.7 0.27

28 Ni ₇₂ Cr ₅ 5SieBi i 75P475 Fluxed 2.9 0.29

29 Ni ₇ i ₅ Cr _{5 5} Si6Bi2P5 Fluxed 2.5 0.5

30 Ni ₇₂ Cr ₅ 5S15.75B11 75P5 Fluxed 2.5 0.5

31 Ni ₇₂ Cr ₅₅ Si ₆ Bi _{! 5} P ₅ Fluxed 2.5 0.5

32 NI71 75Cr575SI5.75B11 75P5 Fluxed 2.5 0.5

33 Ni ₇₂ Cr ₅ 5S15.5B11 75P5.25 Fluxed 2.5 0.5

34 Ni72.25Cr525Si5.75B11 75P5 Fluxed 2.5 0.5

[0063] FIG. 3 provides a data plot of the critical rod diameter for samples 10-13 presented in Table 2 showing the effect of P atomic concentration on the glass-forming ability of the Ni- Cr-Si-B-P alloys according to the formula Ni ₇ i Cr ₆ Sii ₂ - _x B P _x .. By substituting Si by P in the quaternary alloy Ni-Cr-Si-B, the glass-forming ability was found to further improve. As shown in FIG. 3, the critical rod diameter reaches a peak at about 5 % P, wherein the alloy is able to form metallic glass rods of 3.2 mm in diameter when the quartz capillary wall thickness is about 0.32 mm.

[0064] FIG. 4 provides a data plot of the critical rod diameter for samples 1 -9 in Table 1 , and samples 15 and 23-25 in Table 2 showing the effect of Cr atomic concentration on the glass- forming ability of sample Ni-Cr-Si-B and Ni-Cr-Si-B-P alloys according to the formulas Ni ₇₇ . respectively. As shown in FIG. 4, alloys containing 4% P demonstrate considerably better glass-forming ability compared to P-free Ni-Cr-Si-B alloys over a broad Cr range. For example, at 5.5 % Cr, alloy Ni ₇ i (sample 24) has critical rod diameter of about 3.5 mm when the quartz capillary wall thickness is about 0.35 mm, while the P-free Ni ₇ sCrssSi^B alloy (sample 5) has critical rod diameter of about 2 mm when the quartz capillary wall thickness is about 0.2 mm. [0065] FIG. 5 provides calorimetry scans for sample metallic glasses Ni-Cr-Si-B-P with varying P atomic concentrations (sample 6 in Table 1 and samples 10-13 in Table 2) according to embodiments of the present disclosure. As shown, the Ni-Cr-Si-B-P alloys have lower liquidus temperatures than the Ni-Cr-S-B alloys, with a minimum occurring around the P content of 5 %. Arrows in FIG. 5 designate the liquidus temperatures for the alloys with various contents of P. Lower liquidus temperature as illustrated in the calorimetry scan implies an improved potential for glass forming ability.

[0066] FIG. 6 provides data plots of the critical rod diameter for samples 17 and 19-22 in Table 2 showing the effect of varying the combined Si and B atomic concentration with the Ni atomic concentration on the glass-forming ability of sample Ni-Cr-Si-B-P alloys, according to the formula Ni ₉₄ - _x Cr ₆ Sio.5x-4.5Bo.5x ₊ o.5P4- Varying the total metalloid concentration (the sum of Si, B, and P concentrations) reveals a peak in glass-forming ability at the metalloid concentration of 22.5% (sample 21 ), as shown in FIG. 6. The critical rod diameter varies from 1 .75 mm to about 3 mm in a range of metalloid concentration from 21 to 24 atomic percent, revealing a peak at a metalloid concentration of about 22.5 atomic percent.

[0067] FIG. 7 provides calorimetry scans for sample metallic glasses Ni-Cr-Si-B-P with varying metalloid atomic concentrations (samples 17 and 19-22 shown in Table 2) according to embodiments of the present disclosure. Again, the arrows designate the liquidus temperatures. The liquidus temperature is seen to undergo through a slight minimum at the metalloid concentration of 22.5%, where the largest glass forming ability is observed according to FIG. 6.

[0068] In a more refined stage of the experiments, the Ni-Cr-Si-B-P alloys were processed in quartz tubes having 0.5 mm thick walls. As shown in Table 2, six alloys (Samples 29-34) were capable of forming metallic glass rods at least 2.5 mm in diameter when processed in quartz tubes with 0.5 mm walls. These six alloys are better glass formers than the rest of the alloy family because the 2.5 mm rods are formed using quartz tubes having considerably thicker walls (0.5 mm). The alloy having composition Ni72Cr5.5Si5.75Bn .75P5 (Sample 30) is identified as slightly better than the other five as the 2.5 mm rod was found to contain the amorphous phase across the entire rod length, while for the rest of the alloys the amorphous phase was found mostly at the front end of the rod.

[0069] FIG. 8 provides an optical image of a 2.5 mm metallic glass rod of sample metallic glass Ni72Cr5.5Si5.75Bn .75P5 (sample 30 in Table 2).

[0070] FIG. 9 provides an X-ray diffractogram verifying the amorphous structure of a 2.5 mm metallic glass rod having composition Ni72Cr5.5Si5.75Bn .75P5- [0071] FIG. 10 provides a differential calorimetry scan of a sample metallic glass

Ni72Cr5.5Si5.75Bn .75P5 showing the glass transition temperature of the metallic glass of 431 ^Q C and the liquidus temperature of the alloy of 1013 ^Q C, which are designated by arrows. [0072] The metallic glasses Ni-Cr-Si-B or Ni-Cr-Si-B-P were also found to exhibit a remarkable bending ductility. Specifically, under an applied bending load, the disclosed alloys are capable of undergoing plastic bending in the absence of fracture for diameters up to 1 mm . FIG. 1 1 provides an optical image of a plastically bent 1 mm amorphous rod of metallic glass Ni72Cr5.5Si6B .75 4.75 (sample 28 in Table 2).

Ni-Cr-Mo-Si-B-P Alloys and Metallic Glasses

[0073] The alloy composition Ni72Cr5.5Si5.75Bn .75P5 (sample 30) was found capable of forming bulk metallic glass rods with diameters of up to 2.5 mm when processed by water quenching the molten metal contained in a fused silica tube having 0.5 mm wall thickness. The notch toughness of this metallic glass when measured on a 2 mm diameter rod containing a notch with length between 0.75 and 1 .25 mm and root radius between 0.1 and 0.15 mm, was just under 50 MPa m ^{1 2} . Discovering alloying additions that simultaneously improve both the glass-forming ability and toughness of the alloys would be of great technological importance.

[0074] In a further aspect, the alloy or metallic glass is represented by the following formula:

\ _{W0 . _a . _b . _c . _d . _e) Cr o _b S\ _c B _d P _e (1 ) where subscript a is between 3.5 and 6, b is up to 2, c is between 4.5 and 7, d is between 10.5 and 13, and e is between 4 and 6 (subscripts indicate atomic percent).

[0075] Sample metallic glasses (samples 35-39) showing the effect of substituting Cr by Mo, according to the formula Ni72Cr55.xMOxSi5.75B11.75P5, are presented in Table 3 and FIG. 12, along with sample 30. As shown, when the Mo atomic percent is between 0.5 and 1 , metallic glass rods with diameters equal to or greater than 2.5 mm and as high as 3 mm can be formed. The metallic glass rods in Table 3 were processed in fused silica tubes having 0.5 mm wall thickness. Differential calorimetry scans performed at a heating rate of 20 K/min for sample metallic glasses in which Cr is substituted by Mo are presented in FIG. 13.

Table 3: Sample metallic glasses demonstrating the effect of increasing the Mo atomic concentration at the expense of Cr on the glass forming ability of the Ni-Cr-Si-B-P alloy

Example Composition Critical Rod Diameter

[mm]

38 Ni72Cr4.25M01.25Si5.75Bn 75P5 1 .5

39 Ni72Cr4M0L5Si5.75Bn .75 5 1 .5

[0076] Among the compositions in Table 3, the alloys exhibiting the highest glass-forming ability are Examples 36 and 37, having compositions Ni72Cr4.75Mo0.75Si5.75Bn .75 5 and Ni72Cr4.5M01 Si5.75Bn .75P5, respectively. Both alloys are capable of forming metallic glass rods of up to 3 mm in diameter. An image of a 3 mm diameter amorphous

Ni72Cr4.5M01 Si5.75Bn .75P5 rod is shown in FIG. 14. An x-ray diffractogram taken on the cross section of a 3 mm diameter Ni72Cr4.5M01 Si5.75Bn .75P5 (sample 38) rod verifying its amorphous structure is shown in FIG. 15.

[0077] The mechanical properties of the Ni-Cr-Mo-Si-B-P metallic glasses were investigated for sample alloys with various Mo concentrations. The mechanical properties include the compressive yield strength, a _y , which is the measure of the material's ability to resist non- elastic yielding, and the stress intensity factor at crack initiation (i.e. the notch toughness), K _q , which is the measure of the material's ability to resist fracture in the presence of blunt notch. Specifically, the yield strength is the stress at which the material yields plastically, and the notch toughness is a measure of the work required to propagate a crack originating from a blunt notch. Another property of interest is the bending ductility of the material. The bending ductility is a measure of the material's ability to resist fracture in bending in the absence of a notch or a pre-crack. Lastly, another mechanical property of interest is the hardness, which is a measure of the material's ability to resist plastic indentation. These four properties characterize the material mechanical performance under stress. A high o _y ensures that the material will be strong; a high K _q ensures that the material will be tough in the presence of relatively large defects; a high bending ductility ensures that the material will be ductile in the absence of large defects. The plastic zone radius, r _p , defined as K _q ² /na _y ² , is a measure of the critical flaw size at which catastrophic fracture is promoted. The plastic zone radius determines the sensitivity of the material to flaws; a high r _p designates a low sensitivity of the material to flaws. Lastly, a high hardness will ensure that the material will be resistant to indentation and scratching.

[0078] The measured yield strength and notch toughness of sample metallic glasses Ni72Cr55.xMOxSi5.75B11.75P5, where x is 0, 0.5, and 1 (samples 30, 35, and 37), are listed along with the critical rod diameter in Table 4. The plastic zone radii r _p for these metallic glasses are also presented in Table 4. The notch toughness of the metallic glasses appears to increase monotonically with increasing x, going from just under 50 MPa m ^{1 2} for the Mo-free metallic glass to about 65 MPa m ^{1 2} for the metallic glass containing 1 atomic percent Mo. This is shown graphically in FIG. 16. The yield strength appears to increase slightly from 2725 MPa for the Mo-free metallic glass to about 2785 MPa for the metallic glass containing 0.5 atomic percent Mo and back to 2720 MPa for the metallic glass containing 1 atomic percent Mo. The stress-strain diagrams for the three metallic glasses are presented in FIG. 17. The plastic zone radius is roughly constant at about 0.135 mm between the metallic glasses containing 0 and 0.5 atomic percent Mo, as the enhancement in toughness is approximately balanced by the enhancement in strength. However, for the metallic glass containing 1 atomic percent Mo the plastic zone radius of the metallic glass is increased to 0.178 mm, which is a consequence of its enhanced toughness. Lastly, the HV0.5 hardness of metallic glass Ni72Cr4.5M01Si5.75Bn .75 5 is measured to be 768.3 ± 9.6 kgf/mm ² . The hardness of all metallic glass compositions according to the current disclosure is expected to be over 750 kgf/mm ² .

Table 4: Critical rod diameter, notch toughness, yield strength and plastic zone radius of Ni- Cr-Mo-Si-B-P metallic glasses

[0079] The metallic glasses Ni-Cr-Mo-Si-B-P also exhibit a remarkable bending ductility, similar to the Ni-Cr-Si-B-P alloys shown in FIG. 1 1 . Specifically, under an applied bending load, the metallic glasses are capable of undergoing plastic bending in the absence of fracture for diameters up to at least 1 mm. An optical image of a plastically bent metallic glass rod at 1 -mm diameter section of example metallic glass Ni ₇₂ Cr ₄ . ₅ M0 ₁ Si ₅ . ₇₅ Bn . ₇₅ P ₅ is presented in FIG. 18.

[0080] Lastly, the metallic glasses Ni-Cr-Mo-Si-B-P also exhibit a remarkable corrosion resistance. The corrosion resistance of example metallic glass Ni ₇₂ Cr ₄ . ₅ M0 ₁ Si ₅ . ₇₅ Bn _.75 P ₅ is evaluated by immersion test in 6M HCI. The density of the metallic glass rod was measured using the Archimedes method to be 7.9 g/cc. A plot of the corrosion depth versus time is presented inFIG. 19. The corrosion depth at approximately 735 hours is measured to be about 25 micrometers. The corrosion rate is estimated to be 0.33 mm /year. The corrosion rate of all metallic glass compositions according to the current disclosure is expected to be under 1 mm/year.

Description of Methods of Processing the Alloys

[0081] A method for producing the alloys involves inductive melting of the appropriate amounts of elemental constituents in a quartz tube under inert atmosphere. The purity levels of the constituent elements were as follows: Ni 99.995%, Cr 99.996% (single crystal), Mo 99.95%, Si 99.9999%, B 99.5%, P 99.9999%.

[0082] The alloy ingots may be fluxed with a reducing agent such as dehydrated boron oxide (B ₂ 0 ₃ ). A method for fluxing the alloys of the present disclosure involves melting the ingots and B ₂ 0 ₃ in a quartz tube under inert atmosphere, bringing the alloy melt in contact with the B ₂ 0 ₃ melt and allowing the two melts to interact for at least 500 seconds, and in some embodiments 1500 seconds, at a temperature of at least 1 100°C, and in some embodiments between 1200 and 1400°C, and subsequently quenching in a bath of room temperature water.

[0083] A method for producing metallic glass rods from the alloy ingots involves re-melting the fluxed ingots in quartz tubes in a furnace at a temperature of at least 1 100°C, in some embodiments between 1200°C and 1400°C, under high purity argon and rapidly quenching the molten alloy in a room-temperature water bath. The quartz tubes may have a wall thickness ranging from 0.05 mm to 0.5 mm.

[0084] In various embodiments, metallic glasses comprising the alloy of the present disclosure can be produced by: (1 ) re-melting the fluxed ingots in quartz tubes, holding the melt at a temperature of about 1 100 °C or higher, and in some embodiments between 1200°C and 1400°C, under inert atmosphere, and rapidly quenching in a liquid bath; or (2) re-melting the fluxed ingots, holding the melt at a temperature of about 1 100°C or higher, and in some embodiments between 1200°C and 1400°C, under inert atmosphere, and injecting or pouring the molten alloy into a metal mold, which may be made of copper, brass, or steel.

Test Methodology for Differential Scanning Calorimetry

[0085] Differential scanning calorimetry at a scan rate of 20 K/min was performed to determine the glass-transition, crystallization, solidus, and liquidus temperatures of sample metallic glasses.

Test Methodology for Assessing Glass-Forming Ability

[0086] The glass-forming ability of each alloy was assessed by determining the maximum rod diameter in which the amorphous phase can be formed when processed by the method described above. X-ray diffraction with Cu- σ radiation was performed to verify the amorphous structure of the alloys. Images of fully amorphous rods made from the alloys of the present disclosure with diameters ranging from 3 to 10 mm are provided in FIG. 9.

Test Methodology for Measuring Notch Toughness

[0087] The notch toughness of sample metallic glasses was performed on 2-mm diameter metallic glass rods. The rods were notched using a wire saw with a root radius of between 0.10 and 0.13 μιη to a depth of approximately half the rod diameter. The notched

specimens were placed on a 3-point bending fixture with span distance of 12.7 mm and carefully aligned with the notched side facing downward. The critical fracture load was measured by applying a monotonically increasing load at constant cross-head speed of

0.001 mm/s using a screw-driven testing frame. At least three tests were performed, and the variance between tests is included in the notch toughness plots. The stress intensity factor for the geometrical configuration employed here was evaluated using the analysis by

Murakimi (Y. Murakami, Stress Intensity Factors Handbook, Vol. 2, Oxford: Pergamon Press, p. 666 (1987)).

Test Methodology for Measuring Compressive Yield Strength

[0088] Compression testing of sample metallic glasses was performed on cylindrical specimens 2 mm in diameter and 4 mm in length by applying a monotonically increasing load at constant cross-head speed of 0.001 mm/s using a screw-driven testing frame. The strain was measured using a linear variable differential transformer. The compressive yield strength was estimated using the 0.2% proof stress criterion.

Test Methodology for Measuring Hardness

[0089] The hardness was measured using a Vickers microhardness tester. Nine tests were performed where micro-indentions were inserted on a flat and polished cross section of a 2- mm metallic glass rod of composition ₇₅ P ₅ using a load of 500 g and a duel time of 10 s. Test Methodology for Measuring Corrosion Resistance

[0090] The corrosion resistance was evaluated by immersion tests in hydrochloric acid (HCI). A rod of metallic glass Ni72Cr4.5M01 Si5.75Bn .75P5 with initial diameter of 1 .97 mm and length of 19.31 mm was immersed in a bath of 6M HCI at room temperature. The corrosion depth at various stages during the immersion was estimated by measuring the mass change with an accuracy of ±0.01 mg. The corrosion rate was estimated assuming linear kinetics. [0091] The present Ni-Si-B based alloys with additions of Cr, P, or Mo demonstrate better glass forming ability than the Ni-Si-B alloys. Specifically, the present alloys Ni-Cr-Si-B with Cr substituting Ni in the Ni-Si-B alloys have better glass forming ability than the Cr-free Ni-Si- B alloys. The present alloys Ni-Cr-Si-B-P with P substituting Si in the Ni-Cr-Si-B alloys have better glass forming ability than the P-free Ni-Cr-Si-B alloys. The present alloys Ni-Cr-Mo- Si-B-P with Mo substituting Cr in the Ni-Cr-Si-B-P alloys have better glass forming ability than the Mo-free Ni-Cr-Si-B-P alloys. The metallic glasses also demonstrate high strength and hardness, high toughness and bending ductility, as well as high corrosion resistance.

[0092] The combination of high glass-forming ability and the excellent mechanical and corrosion performance of the bulk Ni-based metallic glasses make them excellent candidates for various applications. For example, among many other applications, the present alloys may be used in consumer electronics, dental, medical, luxury goods and sporting goods applications.

[0093] Having described several embodiments, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present disclosure. Accordingly, the above description should not be taken as limiting the scope of the disclosure.

[0094] Those skilled in the art will appreciate that the presently disclosed embodiments teach by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.