JP7565284B2 - Casting alloys for high pressure vacuum die casting - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Application No. 62/796,735, filed January 25, 2019, which is hereby incorporated in its entirety.

This application relates to a casting alloy that exhibits acceptable strength properties after casting.

Alloying of industrially pure aluminum alloys can produce solid solutions or individual phases that significantly improve tensile strength due to solid solution and precipitation strengthening. However, electrical conductivity may decrease due to increased scattering of free electrons in solute atoms and precipitates. For electrical applications, the challenge in alloy design and development is to find a favorable combination of high electrical conductivity and good mechanical properties.

In addition, for applications requiring high pressure vacuum die casting, it is important that the alloy has suitable fluidity for casting into a die and that it has limited hot cracking and die seizure.

It is desirable to have an aluminum alloy with improved casting characteristics, e.g., improved flowability and increased resistance to hot tearing. Alternatively, or in conjunction with the above, it is desirable to have an aluminum conductor alloy with improved electrical conductivity without substantially reducing its mechanical properties.

The present disclosure provides for the use of Ni in low-Si aluminum casting alloys to increase the flow properties of the alloys during casting, limit hot tearing during high pressure vacuum die casting processes, and/or improve die seizure resistance during high pressure vacuum die casting processes.

According to a first aspect, the present disclosure provides a composition comprising, in weight percent:
Ni about 1.5 to about 6.5,
Si about 0.10 to 1.5,
Mg about 0.10 to about 3,
Fe: Maximum approx. 0.2;
Mn maximum about 0.65,
Ti maximum about 0.12,
V Maximum about 0.15,
Zr: maximum about 0.15;
Mo: Maximum about 0.15;
Cr: Maximum approx. 0.01,
Sr Maximum approx. 0.02
Including,
A cast alloy is provided with the balance being aluminum and incidental impurities.

In one embodiment, the casting alloy includes Ni greater than about 2.0. In another embodiment, the casting alloy includes Ni from about 2.5 to about 6.5. In yet another embodiment, the casting alloy includes Ni from about 1.8 to about 3.0. In yet another embodiment, the casting alloy includes Si from 0.15 to 0.90. In yet a further embodiment, the casting alloy includes Si from 0.3 to 0.75. In yet another embodiment, the casting alloy includes a composition represented by formula (I):
Mg content%≦-1.218×ln(Si content%)+0.89 (I)
where Mg% is the weight percent of Mg;
(Si content % is weight percent of Si)
The weight percentage of Mg is determined by:

In one embodiment, the casting alloy includes from about 0.15 to about 1.8 Mg. In yet another embodiment, the casting alloy includes from about 0.30 to about 1.0 Mg. In yet another embodiment, the casting alloy includes a maximum of about 0.10 Fe. In yet another embodiment, the casting alloy includes from about 0.45 to about 0.65 Mn. In yet a further embodiment, the casting alloy includes a maximum of about 0.01 Mn. In yet another embodiment, the casting alloy includes from about 0.02 to about 0.12 Ti. In yet a further embodiment, the casting alloy includes a maximum of about 0.01 Ti. In yet another embodiment, the casting alloy includes a maximum of about 0.01 V. In yet a further embodiment, the casting alloy includes a maximum of about 0.01 V. In yet another embodiment, the casting alloy includes a maximum of about 0.01 Zr to about 0.15 Zr. In yet another embodiment, the casting alloy includes a maximum of about 0.01 Zr. In yet a further embodiment, the casting alloy comprises from about 0.01 to about 0.15 Mo. In another embodiment, the casting alloy comprises a maximum of about 0.01 Mo. In yet another embodiment, the casting alloy comprises from about 0.005 to about 0.02 Sr. In a further embodiment, the casting alloy comprises excess Mg to a weight percent ratio of Mg:Si of greater than about 2:1. In yet a further embodiment, particularly when the aluminum alloy is for use in electrical applications, the casting alloy comprises a metal complex represented by formula (II):
Mn content% + Cr content% + Ti content% + V content%≦0.025 (II)
where Mn content is the weight percent of Mn;
%Cr is the weight percent of Cr;
Ti% is the weight percent of Ti;
V content % is the weight percent of V)
The alloy comprises Mn, Cr, Ti, and V in weight percentages determined by:

According to a second aspect, the present disclosure provides a method of improving at least one casting property of a first aluminum alloy for producing a first aluminum product compared to a cast aluminum alloy for producing a cast aluminum product, the method comprising incorporating Ni into said first aluminum alloy to provide said cast aluminum alloy, said first aluminum alloy comprising, in weight percent:
Si about 0.10 to 1.5,
Mg about 0.10 to about 3,
Fe: Maximum approx. 0.2;
Mn maximum about 0.65,
Ti maximum about 0.12,
V Maximum about 0.15,
Zr: maximum about 0.15;
Mo: Maximum about 0.15;
Cr: Maximum approx. 0.01,
Sr Maximum approx. 0.02
with the balance being aluminum and unavoidable impurities. In the method of the present disclosure, the modified aluminum alloy comprises from about 1.5 to about 6.5 Ni. In one embodiment, the at least one casting property is improved fluidity during casting, reduced hot tearing during high pressure vacuum die casting, and/or improved die seizure resistance. In one embodiment, the modified aluminum alloy comprises at least about 2.0 Ni. In another embodiment, the modified aluminum alloy comprises from about 2.5 to about 6.5 Ni. In another embodiment, the modified aluminum alloy comprises excess Mg for a weight percent ratio of Mg:Si of greater than about 2:1. In yet another embodiment, the modified aluminum alloy comprises from about 1.8 to about 3.0 Ni. In another embodiment, the first aluminum alloy comprises 0.15 to 0.90 Si. In a further embodiment, the first aluminum alloy comprises 0.3 to 0.75 Si. In yet another embodiment, the first aluminum alloy comprises a metal oxide having a formula (I):
Mg content%≦-1.218×ln(Si content%)+0.89 (I)
where Mg% is the weight percent of Mg;
(Si content % is weight percent of Si)
The weight percentage of Mg is determined by:

In a further embodiment, the first aluminum alloy includes from about 0.15 to about 1.8 Mg. In yet another embodiment, the first aluminum alloy includes from about 0.30 to about 1.0 Mg. In yet another embodiment, the first aluminum alloy includes up to about 0.10 Fe. In yet a further embodiment, the first aluminum alloy includes from about 0.45 to about 0.65 Mn. In another embodiment, the first aluminum alloy includes up to about 0.01 Mn. In yet another embodiment, the first aluminum alloy includes from about 0.02 to about 0.12 Ti. In yet another embodiment, the first aluminum alloy includes up to about 0.01 Ti. In another embodiment, the first aluminum alloy includes from about 0.01 to about 0.15 V. In another embodiment, the first aluminum alloy includes up to about 0.01 V. In yet a further embodiment, the first aluminum alloy includes from about 0.01 to about 0.15 Zr. In yet another embodiment, the first aluminum alloy includes up to about 0.01 Zr. In yet a further embodiment, the first aluminum alloy includes from about 0.01 to about 0.15 Mo. In yet yet another embodiment, the first aluminum alloy includes up to about 0.01 Mo. In one embodiment, the first aluminum alloy includes from about 0.005 to about 0.02 Sr. In yet another embodiment, particularly when the modified aluminum alloy is for use in electrical applications, the first aluminum alloy has a structure represented by formula (II):
Mn content% + Cr content% + Ti content% + V content%≦0.025 (II)
where Mn% is the weight percent of Mn;
%Cr is the weight percent of Cr;
Ti% is the weight percent of Ti;
V content % is the weight percent of V)
The alloy comprises Mn, Cr, Ti, and V in weight percentages determined by:

According to a third aspect, the present disclosure provides a modified cast aluminum alloy produced from the method described herein.

According to a fourth aspect, the present disclosure provides a method for producing a cast aluminum product, comprising casting the described cast aluminum alloy or the described modified cast aluminum alloy into a mold. In one embodiment, the method comprises subjecting the described cast aluminum alloy or the described modified die cast aluminum alloy to high pressure vacuum die casting. In another embodiment, the method further comprises a post-casting heat treatment step, such as, for example, a T6 or T5 temper.

According to a fifth aspect, the present disclosure provides a cast aluminum product comprising a cast aluminum alloy as described herein or a modified cast aluminum alloy as described herein. In some embodiments, the cast aluminum product can be manufactured by a method as described herein. In one embodiment, the cast aluminum product is electrically conductive. In another embodiment, the cast aluminum product is a rotor.

Having thus generally described the characteristics of the present invention, reference will now be made to the accompanying drawings, in which preferred embodiments of the invention are shown, by way of example only, in which:

Figure 1 shows the Scheil solidification rate curves for Al-6%Ni alloy (◆), Al-1.8%Fe alloy (▲), Al-1.8%Fe-1%Ni alloy (●), and Al-5%Ni-1.8%Fe alloy (■). The results are shown as a function of temperature as a function of solid mole fraction. FIG. 2 shows the mechanical properties of various alloys in the as-cast and tempered tempers. For the various alloys in the as-cast and tempered tempers, the results of tensile strength (UTS (in MPa), first column for each alloy tested, left axis), yield strength (YS (in MPa), second column for each alloy tested, left axis), quality index (QI (in MPa), grey columns for each alloy tested), or elongation (% elongation, open columns for each alloy tested) are shown. Figure 3 shows the effect of magnesium and silicon content on the as-cast mechanical properties, showing the results of yield strength (◆, in MPa, left axis) and elongation (El, ■, in percent, right axis) as a function of the magnesium and silicon content (weight percent) used. 4 shows the mechanical properties of various alloys in the T5 temper (aged at 210° C. for 1 hour). Results are shown for tensile strength (UTS in MPa, first column for each alloy tested, left axis), yield strength (YS in MPa, second column for each alloy tested, left axis), quality index (QI in MPa, grey columns for each alloy tested), or elongation (percent elongation, open columns for each alloy tested) for the various alloys in the T5 temper. Figure 5 is a micrograph of the as-cast AlNi2Si0.15Mg0.15 alloy. Scale bar = 20 μm. Figure 6 is a micrograph of the as-cast AlNi2Si0.3Mg0.6 alloy. Scale bar = 20 μm. Arrows point to undissolved _Mg2Si from solidification. 7 shows the mechanical properties of various alloys in the T6 temper (solution heat treated at 460° C. or 500° C. for 1 hour, air quenched at 5° C./s, naturally aged at room temperature for 12 hours, aged at 185° C. for 2.5 hours). Tensile strength (UTS in MPa, first column for each alloy tested, left axis), yield strength (YS in MPa, second column for each alloy tested, left axis), quality index (QI in MPa, grey columns for each alloy tested), or elongation (percent elongation, open columns for each alloy tested) results are shown for various alloys in the T6 temper. 8 shows the effect of magnesium and silicon content on the mechanical properties of T6, showing the results of yield strength (YS, ◆, in MPa, left axis) and elongation (El, ■, in percent, right axis) as a function of the magnesium and silicon content (weight percent) used. 9 is a micrograph of the T6 tempered AlNi2Si0.15Mg0.15 alloy. Scale bar = 20 μm. 10 is a micrograph of the T6 tempered AlNi2Si0.15Mg0.3 alloy. Scale bar = 20 μm. 11 is a micrograph of the T6 tempered AlNi2Si0.3Mg0.3 alloy. Scale bar = 20 μm. 12 is a micrograph of the T6 tempered AlNi2Si0.3Mg0.6 alloy. Scale bar = 20 μm. 13 is a micrograph of the T6 tempered AlNi2Si0.3Mg0.6Mn alloy. Scale bar = 20 μm. 14 is a micrograph of the T6 tempered AlNi2Si0.5Mg0.5 alloy. Scale bar = 30 μm. 15 is a micrograph of the T6 tempered AlNi2Si0.9Mg0.8 alloy. Scale bar = 30 μm. FIG. 16 illustrates the electrical conductivity (IACS conductivity) of the alloys tested as a function of Mg+Si content (weight percent) of the alloys in the T6 temper. FIG. 17 shows the electrical conductivity (IACS conductivity) of the alloys tested as a function of the yield strength (in MPa) of the alloys in the T6 temper. 18 shows the mechanical properties of various alloys in the T6 temper (solution heat treated at 500° C. for 1 or 2 hours, air quenched at 5° C./s, naturally aged at room temperature for 12 hours, aged at 185° C. for 2.5 hours). Tensile strength (UTS in MPa, first column for each alloy tested, left axis), yield strength (YS in MPa, second column for each alloy tested, left axis), quality index (QI in MPa, grey columns for each alloy tested), or elongation (percent elongation, open columns for each alloy tested) results are shown for various alloys in the T6 temper. 19 shows the mechanical properties of various alloys in the T6 temper (solution heat treated at 500° C. for 1 or 2 hours, air quenched at 5° C./s, naturally aged at room temperature for 12 hours, aged at 185° C. for 2.5 hours). Results are shown for tensile strength (UTS in MPa, first column for each alloy tested, left axis), yield strength (YS in MPa, second column for each alloy tested, left axis), quality index (QI in MPa, grey column for each alloy tested), or elongation (percent elongation, open column for each alloy tested). FIG. 20 shows electrical conductivity (IACS conductivity) as a function of the alloy's yield strength (in MPa) for various alloys in the T6 temper (solution heat treated at 500° C. for 1 or 2 hours, air quenched at 5° C./sec, naturally aged at room temperature for 12 hours, aged at 185° C. for 2.5 hours). 21 illustrates the mechanical properties of various alloys in the F temper. Results are shown for tensile strength (UTS, in MPa, first column for each alloy tested, left axis), yield strength (YS, in MPa, second column for each alloy tested, left axis), quality index (QI, in MPa, grey columns for each alloy tested), or elongation (percent elongation, open columns for each alloy tested) for the various alloys in the F temper. 22 illustrates the mechanical properties of various alloys in the T5 temper (aged at 210° C. for 1 hour). Results are shown for tensile strength (UTS in MPa, first column for each alloy tested, left axis), yield strength (YS in MPa, second column for each alloy tested, left axis), quality index (QI in MPa, grey columns for each alloy tested), or elongation (percent elongation, open columns for each alloy tested) for various alloys in the T5 temper. 23 shows the mechanical properties of various alloys in the T6 temper (solution heat treated at 500° C. for 1 hour, air quenched at 5° C./s, naturally aged at room temperature for 12 hours, aged at 185° C. for 2.5 hours). Tensile strength (UTS in MPa, first column for each alloy tested, left axis), yield strength (YS in MPa, second column for each alloy tested, left axis), quality index (QI in MPa, grey columns for each alloy tested), or elongation (percent elongation, open columns for each alloy tested) results are shown for various alloys in the T6 temper. 24 is a micrograph of the F-tempered AlNi3Si0.3Mg0.6 alloy. Scale bar = 20 μm. 25 is a micrograph of the T6 tempered AlNi3Si0.3Mg0.6 alloy. Scale bar = 20 μm. FIG. 26 illustrates electrical conductivity (IACS conductivity) as a function of Ni content (weight percent) in the T6 temper. FIG. 27 is a diagram showing a die that causes hot tearing in high pressure vacuum die casting (HPVDC). 28 shows a map of Hot Tearing Index (HTI) susceptibility for wt% Mg as a function of wt% Si. Ranges of HTI values are identified in the regions above.

The present disclosure relates to the use of Ni in Al-Si-Mg alloys (such as 6xxx alloys) to provide cast or foundry alloys. In some embodiments, the casting alloys of the present disclosure can be used in high pressure vacuum die casting to provide cast aluminum products. The presence of Ni in the casting alloys of the present disclosure does not substantially affect the Mg ₂ Si precipitation strengthening mechanism of the alloys (as Ni is inert to Mg and Si and is not believed to affect the formation of Mg ₂ Si precipitates), which advantageously allows the alloys to be cast, limits hot tearing, and improves die seizure resistance when subjected to high pressure vacuum die casting. In some embodiments, the casting alloys of the present disclosure also exhibit increased electrical conductivity and substantially similar mechanical properties (particularly strength and ductility) when compared to control alloys (such as A365.1 alloy).

In the context of the present disclosure, Ni can be added to aluminum alloys for use in casting applications. For example, Ni can be added to 3xxx, 5xxx, or 6xxx series forging alloys to create casting alloys. In some particular embodiments, Ni can be added to 6xxx series forging alloys to create casting alloys. Ni can also be added to aluminum alloys for use in high pressure vacuum die casting applications to limit hot cracking and/or die seizure. For example, Ni can be added to 2xxx, 3xxx, 4xxx, 5xxx, or 6xxx series alloys to limit hot cracking and/or die seizure during high pressure vacuum die casting. In yet another embodiment, Ni can be added to 6xxx series alloys to limit hot cracking and/or die seizure during high pressure vacuum die casting. In the context of this disclosure, Ni should be added in a minimum weight percentage (e.g., 1.5, 1.8, 2.0, 2.5, or greater than 2.5) that will enable castability and, in some embodiments, prevent die seizure, particularly in high pressure vacuum die casting processes.

Ni may be added to the casting alloys of the present disclosure at a weight percentage of about 1.5 to about 6.5. In one embodiment, Ni is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., a minimum of) about 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, or 6.4. In yet another embodiment, Ni is present in the casting alloy of the present disclosure in a weight percentage of about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, or 1.6 or less (e.g., up to the above). In still further embodiments, Ni is present in the casting alloy of the present disclosure at about 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3 , or 6.4 and about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, or 1.6 by weight percent.

In further embodiments, Ni is present in the casting alloy at a weight percentage greater than about 2.0. As shown in the examples below, including Ni at weight percentages greater than 2.0 limits hot tearing and improves die seizure resistance. In such embodiments, Ni can be present in the casting alloy at a weight percentage greater than about 2.0 and up to about 6.5. In further embodiments, Ni may be present in the casting alloys at a weight percentage greater than about 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, or 6.4. In yet another embodiment, Ni may be present in the casting alloys in a weight percentage of up to about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, or 2.1. In yet another embodiment, Ni is present in the casting alloy at about 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, or 6. 4 and can be present in a weight percentage of about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, or 2.1 or less.

In yet another embodiment, Ni is present in the casting alloy at a weight percentage of about 1.8 to 3.0. In one embodiment, Ni is present in the casting alloy of the present disclosure at a weight percentage of at least (e.g., at a minimum) about 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9. In yet another embodiment, Ni is present in the casting alloy of the present disclosure at a weight percentage of about 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, or 1.9 or less (e.g., at a maximum of the above). In still further embodiments, Ni is present in the casting alloys of the present disclosure in a weight percentage between about 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9 and about 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, or 1.9.

In yet another embodiment, Ni can be added to the casting alloy of the present disclosure in a weight percentage of about 2.5 to about 6.5. In one embodiment, Ni is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., a minimum of) about 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, or 6.4. In yet another embodiment, Ni is present in the casting alloy of the present disclosure in a weight percentage of about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, or 2.6 or less (e.g., up to the above). In still further embodiments, Ni is present in the casting alloy of the present disclosure at about 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3 , or 6.4 and about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, or 2.6.

In further embodiments, Ni is present in the cast alloy at a weight percentage greater than about 2.5. In such embodiments, Ni can be present in the cast alloy at a weight percentage greater than about 2.5 and less than or equal to about 6.5. In further embodiments, Ni can be present in the cast alloy at a weight percentage greater than about 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, or 6.4. In yet another embodiment, Ni may be present in the casting alloys in a weight percentage of less than or equal to about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, or 2.6. In yet another embodiment, Ni is present in the casting alloy at about 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, or 6. 4 and may be present in a weight percentage of about 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, or 2.6 or less.

The cast alloys of the present disclosure also contain Si and Mg. In the cast alloys of the present disclosure, the Si and Mg form precipitates (e.g., Mg ₂ Si particles) that are expected to impart certain mechanical properties (particularly strength and ductility) to cast aluminum products that include the cast aluminum alloys of the present disclosure. As is known in the art, the solubility of Si and Mg in an aluminum matrix is co-dependent. In some embodiments, the Mg/Si atomic ratio is between 1 and 2. In some embodiments, in the aluminum alloys of the present disclosure, the weight percentage of Mg is relative to the weight percentage of Si by the following:
Mg content%≦-1.218×ln(Si content%)+0.89 (I)
There is a relationship between

In some embodiments, when the cast aluminum product is in the T6 temper, the Mg and Si contents are related as shown in formula (I). In some embodiments, when the cast aluminum product is in the F temper, the Mg/Si atomic ratio is close to 1.

In further embodiments, Mg is present in excess relative to a 2:1 Mg:Si (weight percentage) ratio. In some embodiments, the Mg:Si ratio is greater than about 2:1. This may be beneficial in some embodiments to reduce the hot tearing index of the aluminum alloy.

Si is present in the casting alloys of the present disclosure in a weight percentage of about 0.10 to about 1.5. It is important that the casting alloys of the present disclosure contain at least about 0.10 Si to form precipitates with Mg, and not more than about 1.5 Si to provide acceptable electrical properties (such as electrical conductivity) and to avoid silicon eutectic formation.

In one embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., at a minimum) about 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, or 1.40. In another embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage of no more than (e.g., at a maximum of) about 1.50, 1.40, 1.30, 1.20, 1.10, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20. In yet another embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage between about 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, or 1.40 and about 1.50, 1.40, 1.30, 1.20, 1.10, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20.

In one embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage of about 0.15 to about 0.90. In one embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., at a minimum) about 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, or 0.80. In another embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage of about 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20 or less (e.g., at a maximum of the above). In yet another embodiment, Si is present in the casting alloy of the present disclosure in a weight percentage between about 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, or 0.80 and about 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20.

In yet another embodiment, Si is present in the casting alloy of the present disclosure at a weight percentage of about 0.30 to about 0.75. In one embodiment, Si is present in the casting alloy of the present disclosure at a weight percentage of at least (e.g., at a minimum) about 0.30, 0.40, 0.50, 0.60, or 0.70. In another embodiment, Si is present in the casting alloy of the present disclosure at a weight percentage of about 0.75, 0.70, 0.60, 0.50, or 0.40 or less (e.g., at a maximum of the above). In yet another embodiment, Si is present in the casting alloy of the present disclosure at a weight percentage between about 0.30, 0.40, 0.50, 0.60, or 0.70 and about 0.75, 0.70, 0.60, 0.50, or 0.40.

Mg is present in the casting alloys of the present disclosure in a weight percentage of about 0.10 to about 3.0. It is important that the casting alloys of the present disclosure contain at least about 0.10 Mg to form precipitates with Si, and not more than about 3.0 Mg to provide acceptable electrical properties (e.g., electrical conductivity). In one embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., a minimum of) about 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, 2.00, 2.10, 2.20, 2.30, 2.40, 2.50, 2.60, 2.70, 2.80, or 2.90. In another embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of about or less than (e.g., up to) 3.00, 2.90, 2.80, 2.70, 2.60, 2.50, 2.40, 2.30, 2.20, 2.10, 2.00, 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.20, 1.10, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20. In yet another embodiment, Mg is present in the casting alloy of the present disclosure at about 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, 2.00, 2.10, 2.20, 2.30, 2.40, 2.50, 2.60, 2.70, 2.80 , or 2.90 and about 3.00, 2.90, 2.80, 2.70, 2.60, 2.50, 2.40, 2.30, 2.20, 2.10, 2.00, 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.20, 1.10, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20 by weight percent.

In one embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of about 0.15 to about 1.8. In one embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., at a minimum) about 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, or 1.70. In another embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of less than or equal to about 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.20, 1.10, 1.00, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20 (e.g., up to the above). In yet another embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage between about 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, or 1.70 and about 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.20, 1.10, 1.00, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, or 0.20.

In one embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of about 0.3 to about 1.0. In one embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of at least (e.g., a minimum of) about 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or 0.90. In another embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage of about 1.00, 0.90, 0.80, 0.70, 0.60, 0.50, or 0.40 or less (e.g., at most the above). In yet another embodiment, Mg is present in the casting alloy of the present disclosure in a weight percentage between about 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or 0.90 and about 1.00, 0.90, 0.80, 0.70, 0.60, 0.50, or 0.40.

In the alloys of the present disclosure, Fe is not included as an alloying element in the cast alloys of the present disclosure, and if detected, is present only as an impurity or trace element. The presence of Fe would be detrimental to the alloys of the present disclosure, as it is expected to favor the brittle AlFeSi phase. However, Fe is a known impurity in the aluminum smelting process, and thus up to 0.20 weight percent Fe is expected in some primary aluminum. In some embodiments, Fe is present in the cast alloys of the present disclosure at a weight percentage of 0.2, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, or 0.10 or less. In some additional embodiments, Fe is present in the cast alloys of the present disclosure at a weight percentage of 0.10 or less.

In some further embodiments, the casting alloys of the present disclosure may include Mn. Mn can be used, for example, to limit die seizure during high pressure casting processes. However, because the presence of Mn can be detrimental to the electrical conductivity of aluminum products that include the present cast aluminum alloys, Mn, if present, is present in the casting alloys of the present disclosure at a weight percentage of 0.65 or less. In some embodiments, Mn is present in the casting alloys of the present disclosure at a weight percentage of about 0.45-0.65. In some embodiments, Mn is present in the casting alloys of the present disclosure at a weight percentage of about 0.01 or less. In some further embodiments, the casting alloys of the present disclosure may not include Mn as an alloying element.

In some further embodiments, the casting alloys of the present disclosure may include Ti. Ti may be used, for example, as a grain refiner. However, because the presence of Ti may be detrimental to the electrical conductivity of aluminum products that include the present casting aluminum alloys, Ti, if present, is present in the casting alloys of the present disclosure at a weight percentage of 0.12 or less. In some embodiments, Ti is present in the casting alloys of the present disclosure at a weight percentage of about 0.02-0.12. In some further embodiments, Ti is present in the casting alloys of the present disclosure at a weight percentage of about 0.01 or less. In some further embodiments, the casting alloys of the present disclosure may not include Ti as an alloying element.

In some further embodiments, the casting alloys of the present disclosure may include V. V may be used, for example, to enhance the mechanical properties of cast aluminum products including the cast aluminum alloys of the present disclosure. However, because the presence of V may be detrimental to the electrical conductivity of aluminum products including the cast aluminum alloys of the present disclosure, V, if present, is present in the casting alloys of the present disclosure at a weight percentage of 0.15 or less. In some embodiments, V is present in the casting alloys of the present disclosure at a weight percentage of about 0.02 to 0.15. In some embodiments, V is present in the casting alloys of the present disclosure at a weight percentage of about 0.01 or less. In some further embodiments, the casting alloys of the present disclosure may not include V as an alloying element.

In some further embodiments, the casting alloys of the present disclosure may include Zr. Zr may be used, for example, to enhance the mechanical properties of cast aluminum products including the casting aluminum alloys of the present disclosure. Zr may be present in the casting alloys of the present disclosure at a weight percentage of 0.15 or less. In some embodiments, Zr is present in the casting alloys of the present disclosure at a weight percentage of about 0.01 to 0.15. In some further embodiments, Zr is present in the casting alloys of the present disclosure at a weight percentage of about 0.01 or less. In some further embodiments, the casting alloys of the present disclosure may not include Zr as an alloying element.

In some further embodiments, the casting alloys of the present disclosure may include Mo. Mo may be used, for example, to enhance the mechanical properties of cast aluminum products including the casting aluminum alloys of the present disclosure. Mo may be present in the casting alloys of the present disclosure at a weight percentage of 0.15 or less. In some embodiments, Mo is present in the casting alloys of the present disclosure at a weight percentage between about 0.01 and 0.15. In some further embodiments, Mo is present in the casting alloys of the present disclosure at a weight percentage of about 0.01 or less. In some further embodiments, the casting alloys of the present disclosure may not include Mo as an alloying element.

In some further embodiments, the cast alloys of the present disclosure may include Sr. Sr may be used, for example, to modify the structure of the cast aluminum alloys of the present disclosure. Sr may be present in the cast alloys of the present disclosure at a weight percentage of 0.02 or less. In alternative embodiments, Sr may be an optional addition to the aluminum alloys. For example, Sr may be present in the cast alloys of the present disclosure at a weight percentage of about 0.005 to 0.02.

In the alloys of the present disclosure, Cr is not included as an alloying element in the cast alloys of the present disclosure, and if detected, is present only as an impurity or trace element. The presence of Cr would be detrimental to the alloys of the present disclosure, as it would be detrimental to the electrical conductivity of the cast alloys. In some embodiments, Cr is present in the cast alloys of the present disclosure in a weight percentage of about 0.01 or less (e.g., up to 0.01).

In the alloys of the present disclosure, Cu is not included as an alloying element in the cast alloys of the present disclosure and, if detected, is present only as an impurity or trace element. The presence of Cu would be detrimental to the alloys of the present disclosure since it is not inert with respect to the Ni and MgSi particles of the cast alloys of the present disclosure. The cast alloys of the present disclosure do not include Cu as an alloying element.

In some embodiments of the casting alloys of the present disclosure, in order to maintain electrical conductivity, it is preferred to limit the contents of Mn, Cr, Ti, and V. Thus, the contents of Mn, Cr, Ti, and V are determined according to formula (II):
Mn content% + Cr content% + Ti content% + V content%≦0.025 (II)
where Mn% is the weight percent of Mn;
%Cr is the weight percent of Cr;
Ti% is the weight percent of Ti;
V content % is the weight percent of V)
may be followed.

In embodiments where the cast alloy is for use in electrical applications or is required to have a particular electrical conductivity, the cast alloy may include B as an optional alloying element. B may be used, for example, to precipitate the Ti and V components of the alloy. In some embodiments, the presence of B may improve electrical conductivity by 1% IACS conductivity.

Grain refiners such as titanium, titanium boride, or titanium carbide may be optionally included in the aluminum alloys of the present disclosure to solidify the aluminum alloy with a perfectly equiaxed fine grain structure. In one embodiment, the grain refiner is in the form of Ti, TiB, or TiC. When TiB is used as the grain refiner, this may result in a B content in the alloy of up to 0.05 wt.%. When TiC is used as the grain refiner, this may result in a C content in the alloy of up to 0.01 wt.%.

The balance of the aluminum alloy of the present disclosure is aluminum (Al) and incidental impurities. In one embodiment, each impurity is present at a maximum of about 0.03 parts by weight, with the total incidental impurities being present at less than about 0.10 parts by weight.

The cast aluminum alloys of the present disclosure may be subjected to various casting processes, including, but not limited to, high pressure vacuum die casting (HPVDC), to provide cast aluminum products. The presence of Ni in the cast aluminum alloys of the present disclosure allows for improved fluidity of the alloy (compared to Ni-free corresponding alloys) at the expense of casting processes (e.g., high pressure casting processes). In some embodiments, the presence of Ni in the cast aluminum alloys of the present disclosure allows for reduced hot tearing and/or improved die seizure resistance during high pressure casting processes (compared to Ni-free corresponding alloys).

The cast aluminum alloys of the present disclosure may be subjected to an HPVDC process to provide cast aluminum products. In one embodiment of the present disclosure, cast aluminum products produced by HPVDC from aluminum alloys of the present disclosure exhibit substantially similar tensile strength, yield strength, quality index, and/or elongation as a corresponding aluminum product produced by HPVDC but using a control aluminum alloy (e.g., derived from alloy A365.1), as well as a higher electrical conductivity than the control alloy.

The present disclosure also provides a method for producing an aluminum product comprising a cast aluminum alloy as described herein. The method includes processing the aluminum alloy or modified aluminum alloy as described herein, or a cast ingot as described herein, in the aluminum product. The processing step may include directly casting the aluminum alloy into a cast product or an intermediate ingot intended for remelting. Thus, in the context of the present disclosure, the term "aluminum product" may refer to a final cast product (e.g., a rotor, etc.) or an intermediate ingot that may be further remelted into an aluminum product of a different shape. In embodiments where the aluminum product is a cast product, the method may also exclude any post-casting treatment (e.g., the product may be provided as-cast or F-tempered). Alternatively, the method may include a post-casting heat treatment, such as, for example, a T5, T6, or T7 treatment (e.g., a solution heat treatment step and an artificial aging treatment step). In embodiments where the aluminum product is a cast product, the cast product may be an automobile part, such as a chassis or a rotor.

In some embodiments, the cast aluminum product is not subjected to a post-casting heat treatment and is F-tempered. In such embodiments, the quality index of the cast aluminum product may be at least about 185 MPa. In further such embodiments, the quality index of the cast aluminum product may be at least about 185, 190, 195, or 200 MPa. In further such embodiments, the yield of the cast aluminum product may be at least about 75, 80, 85, 90, 95, or 100 MPa. In further such embodiments, the UTS of the cast aluminum product may be at least about 200, 205, 210, 215, or 220 MPa. In further such embodiments, the elongation of the cast aluminum product may be at least about 6.5, 7, 7.5, or 8%.

In some further embodiments, when the cast aluminum product is subjected to a T5 temper, the quality index of the product is at least about 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, or 255 MPa. In embodiments where the T5 temper includes an artificial aging treatment at 210° C. for 1 hour, the quality index of the product is at least about 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, or 255 MPa. In such embodiments, the UTS of the cast aluminum product may be at least about 220, 225, 230, 235, 240, or 245 MPa. In further such embodiments, the yield of the cast aluminum product may be at least about 130, 135, 140, 145, 150, or 155. In still further such embodiments, the elongation of the cast aluminum product may be at least about 5, 5.5, or 6%.

In some further embodiments, when the cast aluminum product is subjected to the T6 temper, the quality index of the product is at least about 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, 300, 305, 310, or 315 MPa. In further embodiments, the yield of the cast aluminum product subjected to the T6 temper is at least about 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, or 245 MPa. In yet another embodiment, the cast aluminum product subjected to the T6 temper has a UTS of at least about 250, 255, 260, 265, 270, 275, or 280 MPa. In yet a further embodiment, the elongation of the present cast aluminum product subjected to the T6 temper is at least about 5.5, 6, 6.5, or 7%. In embodiments where the T6 temper comprises a solution heat treatment at 460° C. for 1 hour, an air quench at a rate of 5° C./sec, followed by natural aging at room temperature for 12 hours, and artificial aging at 185° C. for 2.5 hours, the quality index of the cast aluminum product may be at least about 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, or 300 MPa. In an embodiment in which the T6 temper includes a solution heat treatment at 500° C. for 1 hour, an air quench at a rate of 5° C./sec, followed by natural aging at room temperature for 12 hours, and artificial aging at 185° C. for 2.5 hours, the quality index of the cast aluminum product may be at least about 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, or 300 MPa.

In some further embodiments, the electrical conductivity of the T6 tempered aluminum product is at least 40%, 41%, 42%, 43%, 44%, or 45% IACS.

The present invention will be more readily understood by reference to the following examples, which are presented to illustrate the invention, but not to limit its scope.

Example I - Reduction of Hot Tearing Three alloys, Al-Fe, Al-Ni, and Al-Fe-Ni, were selected based on their potential to exhibit eutectic reactions (calculated using Thermocalc). As is evident from the phase diagrams of these alloys (Thermocalc software, database TCAL5), these three systems exhibit eutectic reactions that have been shown to enhance fluidity and limit hot tearing. Scheil solidification rate curves, also determined using Thermocalc, were performed for the eutectic chemistry of the three systems and are shown in Figure 1.

Due to the eutectic reactions in the three systems, the solidus temperature of aluminum is reduced in these systems. Good fluidity is expected from the low solidus temperature and eutectic solidification. With regard to hot tearing, the three alloy systems show a relatively small solidification interval (5-50°C) and a flat solidification rate curve of 87-94% solid. Therefore, low hot tearing susceptibility is predicted. Finally, in light of the ternary phase diagram (Mondolfo L.F., Aluminum Alloys Structure & Properties, 1976, p. 532) and observations during casting trials, the tendency for die seizure was considered to be good for high pressure die casting. From these experiments, it is understood that when nickel exceeds 2%, ternary iron intermetallic compounds are formed on the die surface, thus reducing die seizure.

Example II - Characterization of alloys containing Ni Al-Ni-Mg-Si alloys (see chemical composition in Table 1) were cast on a 250 t Buhler machine. Each variant was degassed with argon for 20 minutes before casting. Fluxing was performed using a Promag SI once a day (once for each of the two alloys) at a rate of 0.5 g salt per kg of aluminum.

The as-cast plates were naturally aged at room temperature for 1 week before mechanical property testing or heat treatment. Two different heat treatments were performed: artificial aging at 210°C for 1 hour (T5 temper) and solution heat treatment at 500°C for 1 hour, air quenched at a rate of 5°C/s followed by natural aging at room temperature for 12 hours and artificial aging at 185°C for 2.5 hours (T6 temper). Standard ASTM E8 size flat bar specimens were cut from the plates after heat treatment.

As shown in Figure 2, in the as-cast temper, A365.1 provides the best combination of strength and ductility. For the other alloys, increasing the amount of magnesium and silicon gradually increases strength while decreasing ductility. Figure 3 shows the effect of silicon and magnesium on the strength and ductility of the above alloys.

The mechanical properties in the T5 temper show a similar trend than the as-cast temper. With increasing amounts of magnesium and silicon, ductility gradually decreases while strength increases (Figure 4). The decrease in ductility is explained by the presence of _Mg2Si constituents that form during solidification. Figures 5 and 6 show the progression of _Mg2Si from the alloy AlNi2Si0.15Mg0.15 to AlNi2Si0.3Mg0.6 in the as-cast structure ( _Mg2Si appears dark black).

As shown in Figure 7, A365.1 gives the best mechanical properties in the T6 temper. However, the alloy AlNi2Si0.3Mg0.6 gives almost equivalent mechanical properties to A365.1. As the amount of magnesium and silicon increases, strength gradually increases while ductility decreases. Figure 8 shows the effect of silicon and magnesium on the strength and ductility of the above alloys in the T6 temper.

Solution treatment at 500° C. for 1 hour allowed for the dissolution of most of the Mg ₂ Si content. As shown in FIGS. 9-15, when the magnesium level was above 0.5%, some microstructural Mg ₂ Si was still visible.

Considering mechanical properties alone, A365.1 remains the best performing alloy. However, 6xxx type alloys can provide similar mechanical properties than A365.1 at lower chemistries, which provide higher electrical conductivity. The measured electrical conductivity is shown in Table 2. For comparison, two A365.1 variants were used: A365.1A (0.31% Mg) and A365.1B (0.79% Mg). The effect of magnesium and silicon content on electrical conductivity is shown in Figures 16 and 17.

The magnesium content of A365.1 used to measure the mechanical properties lies between A365.1A and A365.1B. Therefore, the electrical conductivity of A365.1 would be 39.5-39.8% IACS. Due to the high silicon content of the A365.1 alloy and the need for manganese to avoid die seizure, the electrical conductivity of the A365.1 alloy is significantly lower than the alloys tested. Therefore, the alloy AlNi2Si0.3Mg0.6, which offers similar mechanical properties but significantly higher electrical conductivity than A365.1, would be suitable for high strength and high electrical conductivity applications.

Electrical conductivity follows an inverse relationship with magnesium and silicon content, as well as yield strength. Electrical conductivity decreases in aluminum with higher alloying element contents. Thus, the lower alloying element variants listed above have the highest electrical conductivity but the lowest strength.

The addition of manganese significantly reduces the electrical conductivity of the above alloys. Therefore, the use of manganese to prevent die seizure is not recommended, both in terms of mechanical properties and electrical conductivity.

Boron can be used to precipitate the titanium and vanadium components of the alloy. In some embodiments, the electrical conductivity can be increased by 1% IACS with boron treatment.

Example III - Effect of Solution Treatment The remaining as-cast slabs from Example II on a 250 ton Buhler machine were used to further investigate the effect of solution heat treatment on the mechanical and electrical properties of the 6xxx series alloys in Table 3.

As shown in Figures 18 and 19, solution heat treatment at 500°C for 1 hour, air quenching at a rate of 5°C/sec, followed by natural aging at room temperature for 12 hours, and artificial aging at 185°C for 2.5 hours (T6 temper) were not sufficient to completely dissolve all the _Mg2Si formed during solidification. Therefore, while maintaining the same quenching and aging cycle, a solution heat treatment at 500°C for 2 hours was performed (Figures 18 and 19).

Longer solution heat treatment times had a positive effect on all alloys tested. The yield strength increased by 15-25 MPa without affecting the elongation. Furthermore, the effect of solution heat treatment time on electrical conductivity is shown in Figure 20.

Longer solution heat treatments had no statistically significant effect on the electrical conductivity of all alloys tested, except for the alloy AlNi2Si0.9Mg0.8. Therefore, longer solution heat treatments are preferred to increase strength without affecting electrical conductivity.

Example IV - Effect of Nickel Content From the Al-Ni phase diagram and die casting tests (Example I), it was determined that good die seizure resistance can be achieved above 2% nickel. The 6xxx alloys shown in Table 3 contain enough nickel to prevent die seizure, but at a low level to reduce cost. If more die seizure or flow is still required, the nickel content can be increased. Higher nickel content alloys were cast to ensure that the nickel does not interfere with the precipitation of _Mg2Si . The chemistry of the alloys is shown in Table 4.

The mechanical properties of the alloys in Table 4 are shown in Figures 21 to 23.

In the F temper (Figure 21), strength improved while elongation decreased from the alloy AlNi2Si0.3Mg0.6 to the alloy AlNi3.5Si0.3Mg0.6. The change in mechanical properties may be related to the increasing amount of nickel, but also to the increasing level of magnesium. Yield strength increased by 10-15 MPa for every 0.5% increase in Ni between the alloys containing 2% and 3% nickel. Mechanical properties were stable between the alloys containing 3% and 3.5% nickel.

A similar pattern was observed in the T5 temper (Figure 22). The increased strength was 15-20 MPa for every 0.5% increase in Ni between the alloys containing 2% and 3% nickel, and the mechanical properties were stable between the alloys containing 3% and 3.5% nickel.

In the T6 temper (Figure 23), the strength increased by 40 MPa going from the alloy AlNi2Si0.3Mg0.6 to the alloy AlNi3Si0.3Mg0.6. However, the elongation remained stable. Thus, at higher levels of nickel, the ductility of the alloy was not affected in the T6 temper.

The decrease in ductility observed in the F and T5 tempers, and the stable ductility in the T6 temper, may be explained by the nickel eutectic morphology. Without wishing to be bound by theory, it is believed that the sharp Al-Ni particles from the F temper are spheroidized during solution heat treatment. This may result in improved ductility as shown in Figures 24 and 25. Thus, the nickel can be tailored to the die seizure and flow required for the application.

The effect of nickel content on conductivity in T6 temper (500°C-1 hour, 185°C-2.5 hours) is shown in Figure 26. When nickel is changed from 2% to 3%, the conductivity does not change statistically.

Example V - Hot Tearing Testing The 6xx series alloys are not currently used in the foundry industry due to the high hot tearing potential of these alloys. To optimize the 6xx+Ni alloys, hot tearing tests were performed in a Buhler high pressure die casting press. A specific die as shown in Figure 27 was designed to quantify hot tearing in a die that generates hot tears during high pressure vacuum die casting (HPVDC). The die comprises four thin sections surrounded by risers. The length of the bar specimens are 50, 100, 150, and 200 mm.

The cracks after casting of each bar specimen were evaluated according to four criteria:
- Crack location (near the lower riser, near the upper riser, inside the riser),
- length of crack (full, partial or microcrack),
The bars were inspected according to the severity of the cracks (through the thickness or not), and the presence or absence of cracks through the length of the bars.

Each crack was quantified using the parameters in Table 5.

Each bar is given a score calculated as follows: If cracks occur, the score in Table 5 is given. If no cracks are observed for a particular parameter, a score of 0 is given. The following calculations are then made using the following formulas:
C _b =B(D+ND+C+P+TP)+H(D+ND+C+P+TP)+M

"n" castings were made, therefore an average value was calculated for each length of bar specimen.

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Finally, the overall hot tearing index for the alloy:

was calculated, where "b" is the rating given to a bar of that length. The 50 mm bar was given the highest "b" rating because any cracks that do initiate in this short section indicate a more significant level of hot tearing susceptibility. The b ratings are summarized in Table 6 below.

The ternary alloys in Table 7 were characterized, and the results are shown in FIG.

A low hot tearing index (HTI) is beneficial, whereas alloys with a high HTI are more susceptible to cracking during solidification. The HTI of the alloys tested varied from 10 to 45. For magnesium contents below 0.6%, the HTI increased as the silicon content increased from 0.3 to 0.6% Si, up to a maximum value. At higher silicon (about 1.2%) the HTI decreased. Above magnesium contents of 0.6%, the effect of silicon content on the HTI became less.

From Example III, the peak strength was obtained for the alloys AlNi2Si0.3Mg0.6 and AlNi2Si0.5Mg0.5 with silicon and magnesium contents of about 1%. The optimum strength to conductivity ratio was obtained with Mg:Si ratios between 2:1 and 1:1. This ratio is associated with the precipitation of MgSi and Mg ₂ Si. However, these alloys showed high hot tearing index. From FIG. 28, higher magnesium content was more beneficial for improving HTI than higher silicon content. For example, for the alloy AlNi2Si0.3Mg0.6, the HTI was 30-35. By increasing the Mg content to 1.2%, the HTI was significantly reduced to 10-15. Even if the silicon content was increased to 1.2%, the HTI would only be reduced to 25-30.

Therefore, a high magnesium content is favorable for castability. However, magnesium affects the electrical conductivity of this alloy. Excessive magnesium reduces the electrical conductivity by 5% IACS ("Properties, Physical Metallurgy, and Phase Diagrams, Vol 1, Aluminum", Van Horn, K. R., ed., (American Society for Metals: 1967), p. 174). To obtain good castings while maintaining good electrical conductivity, the chemical composition needs to be optimized. These optimizations are done according to the morphology of the casting.

Although the present invention has been described in terms of specific embodiments thereof, the claims should not be limited to the preferred embodiments described in the examples, but should be interpreted in the broadest possible manner consistent with the detailed description taken as a whole.

Claims (58)

In weight percent,
Ni 1.5-6.5,
Si 0.10~1.5,
Mg 0.10 to 3,
Fe max 0.2,
Mn max 0.65,
Ti max 0.12,
V max 0.15,
Zr max 0.15,
Mo max 0.15,
Cr max 0.01,
Sr Maximum 0.02
Including,
2. A casting alloy for high pressure vacuum die casting , the balance being aluminium and inevitable impurities. The casting alloy of claim 1, containing more than 2.0 Ni. The casting alloy according to claim 1 or 2, containing 2.5 to 6.5% Ni. The casting alloy according to claim 1, containing 1.8 to 3.0% Ni. A casting alloy according to any one of claims 1 to 4, containing 0.15 to 0.90% Si. A casting alloy according to any one of claims 1 to 5, containing 0.3 to 0.75% Si. Formula (I):
Mg content%≦-1.218×ln(Si content%)+0.89 (I)
where Mg% is the weight percent of Mg;
(Si content is weight percent of Si)
A casting alloy according to any one of claims 1 to 6, comprising Mg in a weight percentage determined by: A casting alloy according to any one of claims 1 to 7, containing 0.15 to 1.8 Mg. A casting alloy according to any one of claims 1 to 8, containing 0.30 to 1.0% Mg. A casting alloy according to any one of claims 1 to 9, containing up to 0.10 Fe. A casting alloy according to any one of claims 1 to 10, containing 0.45 to 0.65 Mn. A casting alloy according to any one of claims 1 to 10, containing up to 0.01 Mn. A casting alloy according to any one of claims 1 to 12, containing 0.02 to 0.12 Ti. A casting alloy according to any one of claims 1 to 12, containing up to 0.01% Ti. A casting alloy according to any one of claims 1 to 14, containing 0.01 to 0.15 V. A casting alloy according to any one of claims 1 to 14, containing up to 0.01 V. A casting alloy according to any one of claims 1 to 16, containing 0.01 to 0.15 Zr. A casting alloy according to any one of claims 1 to 16, containing up to 0.01% Zr. A casting alloy according to any one of claims 1 to 18, containing 0.01 to 0.15 Mo. A casting alloy according to any one of claims 1 to 18, containing up to 0.01 Mo. A casting alloy according to any one of claims 1 to 20, containing 0.005 to 0.02 Sr. Formula (II):
Mn content% + Cr content% + Ti content% + V content%≦0.025 (II)
where Mn% is the weight percent of Mn;
%Cr is the weight percent of Cr;
Ti% is the weight percent of Ti;
V content % is the weight percent of V)
A casting alloy according to any one of the preceding claims, comprising Mn, Cr, Ti and V in weight percentages determined by: A casting alloy according to any one of claims 1 to 22, containing excess Mg for a weight percentage ratio of Mg:Si of more than 2:1. 1. A method of improving at least one casting property of a first aluminum alloy for producing a first aluminum product compared to a cast aluminum alloy for producing a cast aluminum product, comprising incorporating Ni into the first aluminum alloy to provide a modified aluminum alloy , the first aluminum alloy having, in weight percent:
Si 0.10~1.5,
Mg 0.10 to 3,
Fe max 0.2,
Mn max 0.65,
Ti max 0.12,
V max 0.15,
Zr max 0.15,
Mo max 0.15,
Cr max 0.01,
Sr Maximum 0.02
Including,
The balance is aluminum and inevitable impurities.
The modified aluminum alloy contains 1.5 to 6.5 Ni;
The method , wherein the modified aluminum alloy is for high pressure vacuum die casting . The method of claim 24, wherein the at least one casting property is improved flowability during casting. The method according to claim 24 or 25, wherein the casting property is reduced hot cracking or improved die seizure resistance during high pressure vacuum die casting. The method according to any one of claims 24 to 26, wherein the modified aluminum alloy contains at least 2.0% Ni. The method according to any one of claims 24 to 27, wherein the modified aluminum alloy contains 2.5 to 6.5% Ni. The method according to any one of claims 24 to 26, wherein the modified aluminum alloy contains 1.8 to 3.0 Ni. The method according to any one of claims 24 to 29, wherein the first aluminum alloy contains 0.15 to 0.90% Si. The method according to any one of claims 24 to 30, wherein the first aluminum alloy contains 0.3 to 0.75% Si. The first aluminum alloy has formula (I):
Mg content%≦-1.218×ln(Si content%)+0.89 (I)
where Mg% is the weight percent of Mg;
(Si content % is weight percent of Si)
The method of any one of claims 24 to 31, comprising Mg in a weight percentage determined by: The method according to any one of claims 24 to 32, wherein the first aluminum alloy contains 0.15 to 1.8 Mg. The method according to any one of claims 24 to 33, wherein the first aluminum alloy contains 0.30 to 1.0 Mg. The method of any one of claims 24 to 34, wherein the first aluminum alloy contains up to 0.10 Fe. The method according to any one of claims 24 to 35, wherein the first aluminum alloy contains 0.45 to 0.65 Mn. The method of any one of claims 24 to 35 , wherein the first aluminum alloy comprises at most 0.01% Mn. The method according to any one of claims 24 to 37, wherein the first aluminum alloy contains 0.02 to 0.12 Ti. The method according to any one of claims 24 to 37, wherein the first aluminum alloy contains a maximum of 0.01% Ti. The method according to any one of claims 24 to 39, wherein the first aluminum alloy contains 0.01 to 0.15 V. The method according to any one of claims 24 to 39, wherein the first aluminum alloy contains up to 0.01 V. The method according to any one of claims 24 to 41, wherein the first aluminum alloy contains 0.01 to 0.15 Zr. The method according to any one of claims 24 to 41, wherein the first aluminum alloy contains up to 0.01% Zr. The method according to any one of claims 24 to 43, wherein the first aluminum alloy contains 0.01 to 0.15 Mo. The method according to any one of claims 24 to 43, wherein the first aluminum alloy contains a maximum of 0.01 Mo. The method according to any one of claims 24 to 45, wherein the first aluminum alloy contains 0.005 to 0.02 Sr. The first aluminum alloy has the formula (II):
Mn content% + Cr content% + Ti content% + V content%≦0.025 (II)
where Mn% is the weight percent of Mn;
%Cr is the weight percent of Cr;
Ti% is the weight percent of Ti;
V content % is the weight percent of V)
The method of any one of claims 24 to 46, comprising Mn, Cr, Ti, and V in weight percentages determined by: The method of any one of claims 24 to 47, wherein the modified aluminum alloy contains excess Mg for a weight percentage ratio of Mg:Si greater than 2:1. A modified cast aluminum alloy produced by the method according to any one of claims 24 to 48. A method for producing a cast aluminum product, comprising casting the cast aluminum alloy according to any one of claims 1 to 23 or the modified cast aluminum alloy according to claim 49 into a mold. The method of claim 50, further comprising subjecting the cast aluminum alloy or modified die cast aluminum alloy to high pressure vacuum die casting. The method of claim 50 or 51, further comprising a post-casting heat treatment step. The method of claim 52, wherein the post-casting heat treatment is a T6 temper. The method of claim 52, wherein the post-casting heat treatment is a T5 temper. A cast aluminum product comprising the cast aluminum alloy according to any one of claims 1 to 22 or the modified cast aluminum alloy according to claim 49. A cast aluminum product manufactured by the method according to any one of claims 24 to 54. The cast aluminum product of claim 55 or 56, which is electrically conductive. The cast aluminum product according to any one of claims 55 to 57, which is a rotor.

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