ALUMINIUM ALLOYS FOR STRUCTURAL AND NON-STRUCTURAL NEAR NET CASTING, AND METHODS FOR PRODUCING SAME

FIELD

[0001] The present invention relates to the field of aluminium alloys. The present invention is an aluminium alloy utilizing zinc, magnesium, and iron as primary alloying elements, and copper, manganese, titanium, boron, zirconium, vanadium, scandium, chromium, strontium, sodium, molybdenum, silicon, nickel and beryllium as possible minor alloying elements. More particularly, the invention relates to an aluminium-based alloy for near net shape casting of structural and non-structural components. Additionally, when cast this aluminium alloy has reasonable corrosion resistance.

BACKGROUND

[0002] Aluminium alloys are widely used in structural components and manufacturing where corrosion resistance and light weight are required, without significantly compromising strength. Many formulations of aluminium alloy exist, all with different properties depending on the formulation of the Al alloy, and the methods used to produce the alloy. Depending on the formulation, certain trade-offs can exist, such as sacrificing toughness for increased strength. Cost and ease of production are also factors when considering the type of aluminium alloy.

SUMMARY OF THE INVENTION

[0003] Aluminium alloys have been developed to enable structural and nonstructural near-net shaped components for automotive and non-automotive industrial application. Any gravity or pressure assisted metal die or sand mould casting process including but not limited to High Pressure Die Casting (HPDC) could be used to manufacture the alloy into near-net shaped components. The manufacturing method may include the assistance of vacuum during the casting process. All components made from the family of alloys proposed herein may be heat-treated to several combinations of temper for improvement in tensile strength, ductility and resistance to corrosion during service.

[0004] This new aluminium alloy provides a formulation that can be used to manufacture components that have high uniaxial tensile properties and fatigue properties, among other material advantages. Compared to the best existing commercial aluminium alloys, this new aluminium allow may be able to attain up to a 200% improvement in strength and elongation when compared to other alloys having similar heat treatment temper conditions. Rather than focusing solely on maximizing singular properties such as strength, while minimizing the deteriorating effect on other properties such as toughness, the present invention considers improving the manufacturing process, while at the same time increasing several key material properties. For example, in manufacturing this aluminium alloy there is a reduced incident of die soldering and improved life of metal mould cavities, as well as improved fluidity and castability. Furthermore, there is improved recyclability and re- claimability of the alloy. In addition, this alloy specifies parameters for a greater number of elements, and allows for a greater range in tolerance for elements used.

[0005] This new alloy has been tested using a variety of compositional variations for the alloy. These have been evaluated for metal and sand mould casting processes, such as high pressure die casting, permanent mould casting (gravity assisted) and sand mould casting, all with positive results.

[0006] The present invention is an aluminium alloy utilizing zinc, magnesium, and iron as primary alloying elements, and copper, manganese, titanium, boron, zirconium, vanadium, scandium, chromium, strontium, sodium, molybdenum, silicon, nickel and beryllium as possible minor alloying elements.

[0007] More particularly, an aluminium based alloy with zinc, magnesium and iron as primary alloying elements for near net shaped casting of structural components consists of one or more of the following essential elements along with Al:

2 to 10 percentage by weight zinc

0.5 to 5 percentage by weight magnesium

0.5 to 5 percentage by weight iron

0 to 4 percentage by weight copper

0 to 0.5 percentage by weight titanium

0 to 0.1 percentage by weight strontium

0 to 0.2 percentage by weight beryllium

0 to 0.5 percentage by weight zirconium 0 to 0.5 percentage by weight vanadium

0 to 0.5 percentage by weight chromium

0 to 0.5 percentage by weight scandium

0 to 0.1 percentage by weight sodium

0 to 0.5 percentage by weight silicon

0 to 1 percentage by weight manganese

0 to 5 percentage by weight nickel

0 to 0.5 percentage by weight boron

0 to 1 percentage by weight molybdenum

Remaining percentage (66.6 to 96) by weight is aluminium

[0008] The alloy may be cast into near net shaped components using a pressure assisted casting process such as High Pressure Die Casting.

[0009] Degassing with an argon or nitrogen gas purge in the liquid metal may also be employed to clean the molten alloy.

[0010] The use of vacuum may also be used in the die casting process to reduce entrapped gas in the casting resulting in improved tensile strength and ductility of the cast component.

[0011] The components manufactured by the casting process either with or without the assistance of vacuum may be heat treated extensively to achieve a variety of tempers. The main strengthening mechanism during heat treatment is one or more of solid solution strengthening and strengthening from precipitation in the primary aluminium phase through solid-state phase transformation. A list of heat treated tempers that the component could be subjected to successfully without any defects is presented below:

[0012] Fx - As-Cast temper F with natural ageing (incubation) at room temperature for x days.

[0013] T4-y - Solutionizing treatment T4 with natural ageing (incubation) at room temperature, y is an numeric identifier to represent the unique details of the T4 heat treatment used for each component. [0014] T5 - Artificial ageing at high temperature of samples in Fx temper.

[0015] T6-y - Near Peak artificial ageing process carried out by thermal assistance at high temperature, y is an numeric identifier to represent the unique details of the T6 heat treatment used for each component.

[0016] T7-y - Artificial ageing process at high temperature for durations that render the components well past the time required for peak strength at any given temperature, y is an numeric identifier to represent the unique details of the T7 heat treatment used for each component.

[0017] A variety of exemplar components were cast using this alloy in pressure assisted casting processes. These included: Small Scale Test Samples (SSTS); Large Scale Test Samples (LSTS); and a Side Impact Door Beam (SIB).

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a better understanding of the various embodiments described herein, and to show more clearly how these various embodiments may be carried into effect, reference will be made, by way of example, to the accompanying drawings which show at least one example embodiment and which will now be briefly described.

[0019] Figure 1 shows a typical casting of the small scale test specimen component consisting of: A - standard thick tensile test specimen; B - standard thin tensile test specimen; C - standard fatigue test specimen; D - standard wear test specimen and E - standard impact strength test specimen.

[0020] Figure 2 shows the dimensions of the small tensile test specimen demarcated as B in Figure 1. The component adheres to the ASTM E8/E8-11 standard for tensile test specimen.

[0021] Figure 3 shows the dimensions of the large tensile test specimen demarcated as A in Figure 1. The component adheres to the ASTM E8/E8-11 standard for tensile test specimen.

[0038] Figure 4 shows the dimensions in millimeters of the fatigue test specimen demarcated as C in Figure 1. The component adheres to the ASTM E466 & E606 standard for fatigue test specimen (Stress and Strain controlled). [0022] Figure 5 shows the dimensions in millimeters of the wear test specimen demarcated as D in Figure 1. The component adheres to the ASTM G65-04 standard for wear test specimen.

[0023] Figure 6 shows the dimensions in millimeters of the impact strength test specimen demarcated as E in Figure 1. The component adheres to the ASTM E23 standard for impact strength test specimen.

[0024] Figure 7 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a thin tensile specimen in from the SSTS component. This image is from a specimen in F temper.

[0025] Figure 8 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a thin tensile specimen in from the SSTS component. This image is from a specimen in T4 temper.

[0026] Figure 9 shows a typical high magnification microstructure image obtained from a light optical microscope showing the primary aluminium phase in light shade and the secondary phases in darker shades. This image is from a specimen in F temper.

[0027] Figure 10 shows a typical casting of the LSTS component consisting of: A - corrosion plate; B - butterfly shear test specimen; C - standard fatigue test flat specimen; D - standard impact strength test specimen; E - standard fatigue test round specimen; F - standard flat tensile test specimen; G - standard thin tensile test round specimen; H - standard tear test specimen

[0028] Figure 11 shows the dimensions in millimeters of the corrosion plate demarcated as A in Figure 10.

[0029] Figure 12 shows the dimensions in millimeters of the butterfly shear test specimen demarcated as B in Figure 10.

[0030] Figure 13 shows the dimensions in millimeters of the tensile test flat specimen demarcated as F in Figure 10. [0031] Figure 14 shows the dimensions in millimeters of the tensile test flat specimen demarcated as H in Figure 10. The component adheres to the ASTM B871 standard for wear test specimen.

[0032] Figure 15 shows Room temperature S - N curve for smooth round fatigue bar shown in Figure 10 with alloy LSTS#1 after T7-6 heat treatment.

[0033] Figure 16 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a round tensile specimen in from the LSTS component. This image is from a specimen in F temper.

[0034] Figure 17 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a flat tensile specimen in from the LSTS component. This image is from a specimen in F temper.

[0035] Figure 18 shows atypical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a round tensile specimen in from the LSTS component. This image is from a specimen in T4 temper.

[0036] Figure 19 shows a typical high magnification microstructure image obtained from a light optical microscope showing the primary aluminium phase in light shade and the secondary phases in darker shades. This image is from a round tensile test specimen in F temper.

[0037] Figure 20 shows a typical high magnification microstructure image obtained from a light optical microscope showing the primary aluminium phase in lighter shades and the secondary phases in darker shades. This image is from a round tensile test specimen in F temper with alloy LSST#5.

[0038] Figure 21 shows a typical casting of the SIB component.

[0039] Figure 22 shows the locations of five (5) tensile test specimens cut and machined from the SIB component.

[0040] Figure 23 shows the dimensions of tensile test flat specimen shown in Figure 20. [0041] Figure 24 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a flat tensile specimen M5 from the SIB component with alloy SIB#1 and manufactured with vacuum assisted HPDC. This image is from a specimen in F temper.

[0042] Figure 25 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a flat tensile specimen M5 from the SIB component with alloy SIB#1 and manufactured without vacuum assisted HPDC. This image is from a specimen in F temper.

[0043] Figure 26 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a flat tensile specimen M5 from the SIB component with alloy SIB#1 and manufactured without vacuum assisted HPDC. This image is from a specimen in T4-3 temper.

[0044] Figure 27 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a flat tensile specimen M3 from the SIB component with alloy SIB#1 and manufactured with vacuum assisted HPDC. This image is from a specimen in T6 temper.

[0045] Figure 28 shows a typical composite microstructure image obtained from a light optical microscope showing the entire cross-section of the gauge section of a flat tensile specimen M5 from the SIB component with alloy SIB#1 and manufactured with vacuum assisted HPDC. This image is from a specimen in T7 temper.

[0046] Figure 29 shows a typical high magnification microstructure image obtained from a light optical microscope showing the primary aluminium phase in light shade and the secondary phases in darker shades.

[0047] Figure 30 shows the schematic illustration (dimensions in inches) of the constrained rod casting (CRC) mold.

[0048] Figure 31 shows the hot tear sensitivity index of Al-5Zn-2Mg alloys with of various Fe contents.

[0049] Figure 32 shows the photographs of the cast component.

DETAILED DESCRIPTION

I. Definitions [0050] Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present application herein described for which they are suitable as would be understood by a person skilled in the art.

[0051] In understanding the scope of the present application, the term

"comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, "including", "having" and their derivatives. The term "consisting" and its derivatives, as used herein, are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The term "consisting essentially of, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps as well as those that do not materially affect the basic and novel characteristic(s) of features, elements, components, groups, integers, and/or steps.

[0052] Terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0053] As used in this application, the singular forms "a", "an" and "the" include plural references unless the content clearly dictates otherwise. For example, an embodiment including "an alloy" should be understood to present certain aspects with one substance or two or more additional substances.

[0054] In embodiments comprising an "additional" or "second" component, such as an additional or second element, the second component as used herein is chemically different from the other components or first component. A "third" component is different from the other, first, and second components, and further enumerated or "additional" components are similarly different. [0055] The term "and/or" as used herein means that the listed items are present, or used, individually or in combination. In effect, this term means that "at least one of or "one or more" of the listed items is used or present.

[0056] Aluminium alloys have been developed to enable structural and non- structural near-net shaped components for automotive and non-automotive industrial application. Any pressure assisted metal die casting process including but not limited to High Pressure Die Casting (HPDC) could be used to manufacture the alloy into near- net shaped components. The manufacturing method may include the assistance of vacuum during the casting process. All components made from the family of alloys proposed herein may be heat-treated to several combinations of temper for improvement in tensile strength, ductility and resistance to corrosion during service.

[0057] This new aluminium alloy provides a formulation that can be used to manufacture components that have high uniaxial tensile properties and fatigue properties, among other material advantages. Compared to the best existing commercial aluminium alloys, this new aluminium allow may be able to attain up to a 200% improvement in strength and elongation when compared to other alloys having similar heat treatment temper conditions. Rather than focusing solely on maximizing singular properties such as strength, while minimizing the deteriorating effect on other properties such as toughness, the present invention considers improving the manufacturing process, while at the same time increasing several key material properties. For example, in manufacturing this aluminium alloy there is a reduced incident of die soldering and improved life of metal mould cavities, as well as improved fluidity and castability. Furthermore, there is improved recyclability and re- claimability of the alloy. In addition, this alloy specifies parameters for a greater number of elements, and allows for a greater range in tolerance for elements used.

[0058] This new alloy has been tested using a variety of compositional variations for the alloy. These have been evaluated for metal and sand mould casting processes, such as high pressure die casting, permanent mould casting (gravity assisted) and sand mould casting, all with positive results.

[0059] The present invention is an aluminium alloy utilizing zinc, magnesium, and iron as primary alloying elements, and copper, manganese, titanium, boron, zirconium, vanadium, scandium, chromium, strontium, sodium, molybdenum, silicon, nickel and beryllium as possible minor alloying elements.

[0060] More particularly, an aluminium based alloy with zinc, magnesium and iron as primary alloying elements for near net shaped casting of structural components consists of one or more of the following essential elements along with Al:

2 to 10 percentage by weight zinc

0.5 to 5 percentage by weight magnesium

0.5 to 5 percentage by weight iron

0 to 4 percentage by weight copper

0 to 0.5 percentage by weight titanium

0 to 0.1 percentage by weight strontium

0 to 0.2 percentage by weight beryllium

0 to 0.5 percentage by weight zirconium

0 to 0.5 percentage by weight vanadium

0 to 0.5 percentage by weight chromium

0 to 0.5 percentage by weight scandium

0 to 0.1 percentage by weight sodium

0 to 0.5 percentage by weight silicon

0 to 1 percentage by weight manganese

0 to 5 percentage by weight nickel

0 to 0.5 percentage by weight boron

0 to 1 percentage by weight molybdenum

Remaining percentage (66.6 to 96) by weight is aluminium

[0061] The alloy may be cast into near net shaped components using a pressure assisted casting process such as High Pressure Die Casting.

[0062] Degassing with an argon or nitrogen gas purge in the liquid metal may also be employed to clean the molten alloy. [0063] The use of vacuum may also be used in the die casting process to reduce entrapped gas in the casting resulting in improved tensile strength and ductility of the cast component.

[0064] The components manufactured by the casting process either with or without the assistance of vacuum may be heat treated extensively to achieve a variety of tempers. The main strengthening mechanism during heat treatment is one or more of solid solution strengthening and strengthening from precipitation in the primary aluminium phase through solid-state phase transformation. A list of heat treated tempers that the component could be subjected to successfully without any defects is presented below:

[0065] Fx - As-Cast temper F with natural ageing (incubation) at room temperature for x days.

[0066] T4-y - Solutionizing treatment T4 with natural ageing (incubation) at room temperature, y is an numeric identifier to represent the unique details of the T4 heat treatment used for each component.

[0067] T5 - Artificial ageing at high temperature of samples in Fx temper.

[0068] T6-y - Near Peak artificial ageing process carried out by thermal assistance at high temperature, y is an numeric identifier to represent the unique details of the T6 heat treatment used for each component.

[0069] T7-y - Artificial ageing process at high temperature for durations that render the components well past the time required for peak strength at any given temperature, y is an numeric identifier to represent the unique details of the T7 heat treatment used for each component.

[0070] A variety of exemplar components were cast using this alloy in pressure assisted casting processes. These included: Small Scale Test Samples (SSTS); Large Scale Test Samples (LSTS); and a Side Impact Door Beam (SIB).

II. EXAMPLES

[0071] The following non-limiting examples are illustrative of the present application: [0072] One embodiment of the alloy consists of casting a thin walled part with composition of Al containing: 5wt.%Zn; 2wt.%Mg; 0.35wt.%Cu; and, 1.5wt.%Fe. The casting process is high pressure die casting without vacuum assistance with the final part having a yield strength, ultimate tensile strength and elongation of 200 MPa, 315 MPa and 3.80% respectively in the as-cast state with 21 days of natural ageing.

[0073] Another embodiment of the alloy consists of casting a LSTS with composition of Al-5wt.%Zn-2wt.%Mg-1.5wt.%Fe. The casting process is high pressure die casting with vacuum assistance with the final part having a yield strength, ultimate tensile strength and elongation of 201 MPa, 312 MPa and 4.63% respectively in the as- cast state.

[0074] Heat treatment (any combination of solution only, incubation only, age only, no treatment or two or more heat treatment steps together) methods could include one or more of the following:

a) One Step Solutionizing: 460C for 3.5 hr to 24 hr with water quench b) Two Step Solutionizing: 450C for 12-22 hr + 5-30 C/h to 475-500C +

475-500C for 4-7 hr with water quench

c) Incubation between solution and age: 1-24 hr at room temperature d) Age (one step): 120-170C for 1-24 hr

e) Age (two step): 120-170C for 1-24 hr + 120-170C for 1-24 hr SMALL-SCALE TEST SPECIMEN (SSTS)

Alloy Compositions

[0075] The following alloy compositions were used in the manufacturing of the small-scale test specimen (SSTS) component.

[0076] Table 1 : The list of typical alloy composition used to cast the SSTS component

Alloy Zn Mg Cu Fe Si Mn Zr Ni Al

Percentage by Weight

SSTS #1 6.02 2.24 0.07 1.67 0 0.02 0 0 Bal.

SSTS #2 6.17 2.22 0.07 1.83 0 0.02 0 0 Bal.

SSTS #3 5.90 2.21 0.07 1.75 0 0.02 0 0 Bal.

SSTS #4 5.56 2.08 0.07 3.78 0 0.03 0 0 Bal. SSTS #5 6.86 2.22 0.08 2.37 0 0.19 0 0 Bal.

SSTS #6 5.92 2.15 0.38 1.62 0 0.24 0 0 Bal.

SSTS #7 4.74 2.1 0.05 1.56 0 0.02 0 0 Bal.

SSTS #8 HD2 2.17 0.082 2.64 0.97 10.13 0.21 0.013 0.097 Bal

(comparative

example alloy)

SSTS Silafont 0.10 0.16 0.03 0.15 10 0.51 0 0 Bal.

36

#9(comparative

example alloy)

Component

[0077] The Figure 1 shows the photograph of a typical SSTS component. The details of each of the five (5) types of test specimen in the component shown in Figure 1 is elaborated in Figure 2 to Figure 6.

Casting Process

[0078] The Table 2 presents the general details of the casting process used to manufacture the SSTS component shown in Figure 1.

[0079] Table 2: The casting process used to manufacture the SSTS component shown in Figure 1.

Heat Treatment

[0080] The various heat treatment tempers that the SSTS was subjected to are listed in Table 3.

x day(s) at

Fx room N/A N/A N/A

temperature

460 °C for 24

T4 N/A N/A N/A

h

460 °C for 24 120°C for 2 h,

T6-1 N/A 24 h

h 160°C for l h

460 °C for 24 120°C for 2 h,

T6-2 N/A 24 h

h 160°C for 2 h

460 °C for 24 120°C for 2 h,

T6-3 N/A 24 h

h 160°C for 3 h

Mechanical Properties

[0081] The Table 4 shows the typical mean mechanical properties obtained from uniaxial tensile tests carried out on the SSTS component at various heat treatment tempers.

[0082] Table 4: The various heat treatment that the SSTS components were subjected to after being cast and prior to evaluation of mechanical properties.

Elongation to

Ultimate

Heat Fracture

Tensile 0.2% Proof

Alloy Treatment (percentage

Strength Stress (MPa)

Temper increase in

(MPa)

gauge length)

SSTS #1 Fii 328 228 4.37

SSTS #2 Fl2 333 232 4.46

SSTS #3 Fl3 341 233 4.93

SSTS #4 Fl2 340 238 4.32

SSTS #5 Fl4 344 253 3.35

SSTS #6 Fl3 349 240 4.32

SSTS #7 Fl3 330 197 7.42

SSTS #8

(comparative Fl3 302 145 2.97 example alloy)

SSTS #9

(comparative Fl3 261 123 6.26 example alloy)

SSTS #4 T4 387 276 4.79

SSTS #5 T4 400 299 3.91

SSTS #6 T4 410 286 5.96

SSTS #7 T4 394 238 9.98

SSTS #4 T6-1 481 439 2.07

SSTS #4 T6-2 483 451 1.51

SSTS #4 T6-3 483 458 1.26 SSTS #5 T6-1 510 474 1.54

SSTS #5 T6-2 543 503 1.79

SSTS #5 T6-3 515 498 1.11

SSTS #6 T6-2 512 464 1.94

SSTS #6 T6-3 511 468 1.70

SSTS #7 T6-1 412 348 4.41

SSTS #7 T6-2 436 396 2.52

SSTS #7 T6-3 442 404 2.63

Microstructure

[0083] Typical microstructure images for the SSTS casting are shown for selected alloys in Figures 7-9.

Salient Features

[0084] None of the alloys shown in Table 1 exhibited any die soldering or die sticking tendencies on to the HI 3 tool steel material of the die.

[0085] The HI 3 tool steel die material did not exhibit any tendencies for heat checking when used with any of the alloys shown in Table 1.

[0086] All the castings of SSTS component were of acceptable integrity and quality as per conventional commercial casting industry wisdom; with no observable visual defects, filling issues or mis-runs.

LARGE-SCALE TEST SPECIMEN (LSTS)

Alloy Compositions

[0087] The following alloy compositions were used in the manufacturing of the large-scale test specimen (LSTS) component.

[0088] Table 5: The list of typical alloy composition used to cast the

LSTS component

Component

[0089] The Figure 10 shows the photograph of a typical LSTS component. The details of new four (4) types of test specimen in the component shown in Figure 10 are elaborated in Figure 11 to Figure 14.

Casting Process

[0090] The Table 6 presents the general details of the casting process used to manufacture the LSTS component shown in Figure 10.

[0091] Table 6: The casting process used to manufacture the LSTS component shown in Figure 10.

Heat Treatment

[0092] The various heat treatment tempers that the LSTS was subjected to listed in Figure 7.

[0093] Table 7: The various heat treatment that the LSTS components were subjected to after being cast and prior to evaluation of mechanical properties.

475 °C for 3.5

T4-4 N/A h, water N/A N/A

quenched

450°C for 12

h, 5°C/h to

T4-5 N/A 475°C, 475°C N/A N/A

for 7 h, water

quenched

450°C for 12

h, 5°C/h to

120°C for 24 h,

T6 N/A 475°C, 475°C 24h

170°C for 3 h for 7 h, water

quenched

460 °C for 24

120°C for 1 h,

T7-1 N/A h, water 24 h

170°C for 6 h quenched

460 °C for 24

120°C for 1 h,

T7-2 N/A h, water 24 h

160°C for 20 h quenched

460 °C for 24

120°C for 24 h,

T7-3 N/A h, water 24 h

160°C for 10 h quenched

460 °C for 24

120°C for 24 h,

T7-4 N/A h, water 24 h

160°C for 24 h quenched

450°C for 12

h, 5°C/h to

120°C for 24 h,

T7-5 N/A 475°C, 475°C 24 h

170°C for 14h for 7 h, water

quenched

450°C for 12

h, 5°C/h to

120°C for 24 h,

T7-6 N/A 475°C, 475°C 24 h

170°C for 24 h for 7 h, water

quenched

Mechanical Properties

[0094] The Table 8 shows the typical mean mechanical properties obtained from uniaxial tensile tests carried out on the LSTS component at various heat treatment tempers. [0095] Table 8: The various heat treatment that the LSTS components were subjected to after being cast and prior to evaluation of mechanical properties.

Figure 15 shows the room temperature fatigue property of smooth round fatigue bar with alloy LSTS#1 after T7-6 heat treatment.

Microstructure

[0096] Typical microstructure images for the LSTS casting are shown for selected alloys in Figure 16-20.

Salient Features [0097] None of the alloys shown in Table 5 exhibited any die soldering or die sticking tendencies on to the P20 tool steel material of the die.

[0098] The P20 tool steel die material did not exhibit any tendencies for heat checking when used with any of the alloys shown in Table 5.

[0099] All the castings of LSTS component were of acceptable integrity and quality as per conventional commercial casting industry wisdom; with no observable visual defects, filling issues or mis-runs.

SIDE IMPACT DOOR BEAM (SIB)

Alloy Compositions

[00100] The following alloy compositions were used in the manufacturing of the side impact door beam (SIB) component.

[00101] Table 9: The list of typical alloy composition used to cast the SIB component

Component

[00102] The Figure 19 shows the photograph of a typical SIB component. The locations of the tensile bars in the SIB component and its dimensions are shown in Figure 20 to 21.

Casting Process

[00103] The Table 10 presents the general details of the casting process used to manufacture the SIB component shown in Table 19.

[00104] Table 10: The casting process used to manufacture the SIB component shown in Figure 19.

Item Description

Casting Machine 1 High Pressure Die Casting Machine without

vacuum assisted Casting Machine 2 Buhler Carat 105L High Pressure Die

Casting Machine with vacuum assisted

Die Tool material P20 tool steel

Metal cleanliness Degassing with Nitrogen gas

Metal temperature 680 °C to 735 °C

Vacuum No vacuum with Casting Machine 1

Vacuum Assist with Casting Machine 2

Heat Treatment

[00105] The various heat treatment tempers that the SIB was subjected to are listed in Table 11.

[00106] Table 11 : The various heat treatment that the SIB components subjected to after being cast and prior to evaluation of mechanical properties.

for 7 h, water

quenched

450°C for 12 h,

5°C/h to

120°C for 24 h,

T7-2 N/A 475°C, 475°C 24 h

170°C for 24 h for 7 h, water

quenched

Mechanical Properties

[00107] The Table 12 shows the typical mean mechanical properties obtained from uniaxial tensile tests carried out on the SIB component at various heat treatment tempers.

[00108] Table 12: The various heat treatment that the SIB components were subjected to after being cast and prior to evaluation of mechanical properties.

Microstructure

[00109] Typical microstructure images for the SIB casting for selected alloys are shown in Figure 22 to 27.

Salient Features

[00110] None of the alloys shown in Table 9 exhibited any die soldering or die sticking tendencies on to the P20 tool steel material of the die. [00111] The P20 tool steel die material did not exhibit any appreciable tendencies for heat checking when used with any of the alloys shown in Table 9.

[00112] All the castings of SIB component were of acceptable integrity and quality as per conventional commercial casting industry wisdom; with no observable visual defects, filling issues or mis-runs.

HOT TEAR SENSITIVITY INDEX (HTS)

[00113] Hot tear sensitivity index of Al-Zn-Mg and Al-Zn-Mg-Fe alloys were evaluated with the Constrained Rod Casting (CRC) mould.

[00114] The CRC mould is made of cast iron (Figure 28), and capable of producing four cylindrical constrained rods with the lengths of 2" (bar A), 3.5" (bar B), 5" (bar C), and 6.5" (bar D) and 0.5" diameter. The bars are constrained at one end by a sprue and at the other end by a spherical riser (feeder) of 0.75" in diameter.

[00115] The value of HTS is given by

D

HTS ^(Q x L _t

i=A

[00116] Where C is the assigned numerical value for the severity of crack in the bars (Table 13), L is the assigned numerical value corresponding to the length of the bar (Table 14), and represents the bars A, B, C, and D.

[00117] Tablel3: The Numerical Values C _; that Represent Crack Severity

[00118] Table 14: The Numerical Values L _; that Represent Bars of Different

Lengths

Alloy compositions

[00119] The following alloy compositions were used to evaluate the hot tear sensitivity as listed in Table 15.

[00120] Tablel5: The list of alloy composition used to cast the HTS samples

Casting process

[00121] One kilogram of each alloy in the Table 15 was melted and degassed with high pure Argon gas for 20 minutes. The pouring temperature was kept at 720°C for all the samples. The CRC mould was preheated at 300°C before pouring. Each alloy had two hot tear samples.

HTS results

[00122] As shown in Figure 29, without Fe addition, Al-Zn-Mg alloy has a high sensitivity to hot tearing. While adding Fe into Al-Zn-Mg, the hot tearing sensitivity of Al-Zn-Mg alloy was alleviated greatly. The HTS index decreases to 1.67 at the addition of 1.3 wt% of Fe.

PILOT SCALE TRIALS

[00123] One of the prescribed compositions of the alloy was used to carry out a pilot production scale trial at an automotive casting facility to manufacture a structural component for a car. The alloy composition used was Al-5wt%Zn-1.6wt%Mg- lwt%Fe-0.05wt%Ti.

[00124] The salient details of the casting process are below:

[00125] Part: Automotive Shock Tower [00126] Amount of Alloy Melted: -10,000 kg

[00127] Melt Temp: 690-730°C

[00128] Degassing: Rotary degasser using industrial purity Ar for 10 minutes

[00129] Vacuum System: 3 chill blocks on die

[00130] Composition (wt.%): Al-5.0Zn-l.6Mg-l .0Fe-0.05Ti

[00131] Number of Crack-free Parts Cast: (not including warm-up shots)

[00132] Primary Alloy: 180

[00133] 50% Remelted Alloy: 80

[00134] 100% Remelted Alloy: 110

[00135] In addition to manufacturing defect free sound castings in a production setting, the other salient advantages from using this new alloy was the significant reduction in die soldering tendencies on the HI 3 die tool and the 100% re-usability of the alloy composition. The mean uniaxial tensile properties of the as-cast component measured in samples from various locations within each component and obtained from several cast components is:

[00136] UTS = 263 MPa

[00137] YS = 145 MPa

[00138] %E1 = 8.2%

[00139] Notably, the properties did not have any variation among the primary, 50% recycled and 100% recycled initial alloy metal. Further, all the parts were heat treatable to solutionizing temperatures without any discemable blistering. These salient properties and observations enable the use of the new alloy in structural automotive component manufacturing.

[00140] Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the application, are given by way of illustration only and the scope of the claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the description as a whole. [00141] While the present application has been described with reference to examples, it is to be understood that the scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[00142] All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.

FULL CITATIONS FOR DOCUMENTS REFERRED TO IN THE

APPLICATION

ASTM E8/E8M-1 l a Standard Test Methods for Tension Testing of Metallic Materials, ASTM International, West Conshohocken, PA, 2011

ASTM E466-15 Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials, ASTM International, West Conshohocken, PA, 2015

ASTM E606 E606M-12 Standard Test Method for Strain-Controlled Fatigue Testing, ASTM International, West Conshohocken, PA, 2012

ASTM G65-04 Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus, ASTM International, West Conshohocken, PA, 2004

ASTM E23-16b Standard Test Methods for Notched Bar Impact Testing of Metallic Materials, ASTM International, West Conshohocken, PA, 2016