CROSS REFERENCE TO RELATED APPLICATION

This U.S. Continuation-In-Part (CIP) Patent Application claims the benefit of U.S. Utility patent application Ser. No. 17/366,175, filed on Jul. 2, 2021, the entire disclosures of the applications being considered part of the disclosure of this application and hereby incorporated by reference.

BACKGROUND OF THE INVENTION
1. Field of the Invention

The invention relates generally to an aluminum alloy for casting, a method of forming the aluminum alloy, a vehicle component formed of the cast aluminum alloy, and a method of manufacturing the cast component.

2. Related Art

Casting of aluminum alloys is oftentimes used in the automotive industry to form lightweight components, including complex structural, body-in-white, suspension, and chassis components. There are many types of known casting processes, for example, high pressure die casting, low pressure casting, and squeeze casting. The die is typically formed of a hardened tool steel. Although the casting equipment is expensive, the cost per component formed is relatively low, which makes the process suitable for high volume production.

However, improvements to the casting process and materials used in the casting process are desired. For example, an aluminum alloy capable of forming a component having higher ductility, without loss of fluidity or castability, is desired. The aluminum alloy should also be resistant to damage associated with hot cracking, soldering, shrinkage, and corrosion. In addition, although lightweight components are desired, the components should still provide a high strength and toughness.

SUMMARY

One aspect of the invention provides an improved aluminum alloy, comprising: at least 80 weight percent (wt. %) aluminum; 9.5 to 11.5 wt. % silicon; 1.5 max wt. % zinc, for example 0.3 to 0.8 wt. % zinc; 0.1 wt. % to 0.6 wt. % magnesium; 0.10 wt. % to 0.60 wt. % copper, or 0.20 wt. % to 0.90 wt. % copper; 0.2. to 0.6 wt. % manganese, for example 0.2. to 0.5 wt. % manganese; 0.2 wt. % to 0.6 wt. % iron, for example 0.3 wt. % to 0.6 wt. % iron; 0.01 wt. % to 0.07 wt. % strontium; and up to 0.15 wt. % titanium, based on the total weight of the improved aluminum alloy.

Another aspect of the disclosure provides a cast component formed of the improved aluminum alloy.

Yet another aspect of the disclosure provides a method of manufacturing an improved aluminum alloy. The method comprises the steps of: obtaining recycled aluminum or a recycled aluminum alloy; and combining the recycled aluminum or the recycled aluminum alloy with at least one additional element to form the improved aluminum alloy, the improved aluminum alloy comprising: at least 80 weight percent (wt. %) aluminum; 9.5 to 11.5 wt. % silicon; 1.5 max wt. % zinc, for example 0.3 to 0.8 wt. % zinc; 0.1 wt. % to 0.6 wt. % magnesium; 0.10 wt. % to 0.60 wt. % copper, or 0.20 wt. % to 0.90 wt. % copper; 0.2. to 0.6 wt. % manganese, for example 0.2. to 0.5 wt. % manganese; 0.2 wt. % to 0.6 wt. % iron, for example 0.3 wt. % to 0.6 wt. % iron; 0.01 wt. % to 0.07 wt. % strontium; and up to 0.15 wt. % titanium, based on the total weight of the improved aluminum alloy.

Another aspect of the disclosure provides a method of manufacturing a cast component. The method comprises the steps of: obtaining recycled aluminum or a recycled aluminum alloy; and combining the recycled aluminum or the recycled aluminum alloy with at least one additional element to form an improved aluminum alloy, the improved aluminum alloy comprising: at least 80 weight percent (wt. %) aluminum; 9.5 to 11.5 wt. % silicon; 1.5 max wt. % zinc, for example 0.3 to 0.8 wt. % zinc; 0.1 wt. % to 0.6 wt. % magnesium; 0.10 wt. % to 0.60 wt. % copper, or 0.20 wt. % to 0.90 wt. % copper; 0.2. to 0.6 wt. % manganese, for example 0.2. to 0.5 wt. % manganese; 0.2 wt. % to 0.6 wt. % iron, for example 0.3 wt. % to 0.6 wt. % iron; 0.01 wt. % to 0.07 wt. % strontium; and up to 0.15 wt. % titanium, based on the total weight of the aluminum alloy. The method further comprises casting the improved aluminum alloy.

Another aspect of the disclosure provides an improved aluminum alloy comprising at least 80 weight percent (wt. %) aluminum; 9.5 to 11.5 wt. % silicon; zinc; 0.1 wt. % to 0.6 wt. % magnesium; copper; at least 0.2. wt. % manganese; up to 0.6 wt. % iron; 0.01 wt. % to 0.07 wt. % strontium; and up to 0.15 wt. % titanium, based on the total weight of the improved aluminum alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 illustrates a raw material, specifically a portion of a cast ingot, formed of an aluminum alloy according to an embodiment of the invention;

FIG. 2 illustrates a portion of a component formed of an aluminum alloy according to an embodiment of the invention;

FIG. 3A discloses examples of different scrap streams, including post-consumer recycled road wheels and pre-consumer wrought stamping offal which can be combined in certain ratios to form an aluminum alloy and cast parts formed of the aluminum alloy according to example embodiments;

FIGS. 3B-3D illustrate cast parts formed of the aluminum alloy according to example embodiments;

FIG. 4 illustrates a chemical composition of an aluminum alloy according to an example embodiment of the invention (Aural 2R) relative to a comparative aluminum alloy (Aural 2);

FIG. 5A is a chart and FIG. 5B is a table illustrating mechanical properties of the aluminum alloy compositions of FIG. 4;

FIGS. 6A and 6B are pictures and FIG. 6C is a table illustrating results of a rivetability test comparting the aluminum alloy compositions according to FIG. 4;

FIGS. 7 and 8 are results of a corrosion testing on the improved aluminum alloy according to an example embodiment and a comparative aluminum alloy.

DESCRIPTION OF THE ENABLING EMBODIMENT

One aspect of the invention provides an improved aluminum alloy for casting components, such as a lightweight automotive vehicle component, is provided. Examples of such components include structural, body-in-white, suspension, or chassis components. The aluminum alloy provides a component with improved ductility and elongation, and without hot tearing or loss of fluidity or castability. The aluminum alloy is also less expensive than other aluminum alloys used for casting, which is especially beneficial for high volume production. An example of a component 10 formed of the aluminum alloy according to example embodiments is shown in FIGS. 2 and 3B-3D.

The improved aluminum alloy is aluminum-based, and thus typically includes aluminum in an amount of at least 80 weight percent (wt. %), based on the total weight of the aluminum alloy. The aluminum alloy also includes an amount of silicon (Si), which helps achieve improved castability of the aluminum alloy and thus reduces a scrap rate and reduces costs. Besides the large amount of silicon eutectic phase, after the T7 heat treatment, the elongation of the component formed of the aluminum alloy is typically 10% to 20%. The castability, strength, and toughness of the aluminum alloy can also be adjusted based on the amount of silicon.

Additional alloying elements can also be present in the improved aluminum alloy to further improve elongation and ductility, or to achieve the desired strength and toughness. For example, magnesium (Mg), manganese (Mn), and/or iron (Fe) can be added to further improve ductility, castability, strength, ductility, and/or toughness. In particular, the manganese can be used to prevent die sticking, and the magnesium can be used to form Mg₂Si for strengthening. The aluminum alloy can also include certain amounts of copper (Cu) and zinc (Zn) to increase strength, preferably without negatively impacting corrosion resistance. The zinc is also used as a solid solution strengthener and to improve machinability. The additional alloying elements can provide other metallurgical effects as well, such as improved resistance to hot cracking, soldering, shrinkage, and corrosion. Strontium (Sr) can also be added to modify the silicon eutectic morphology which affects the ductility that occur due to the silicon that occur due to the silicon.

According to a first example embodiment, in addition to at least 80 wt. % aluminum, the aluminum alloy includes 9.5 to 11.5 wt. % silicon; 0.1 wt. % to 0.6 wt. % magnesium; 0.10 wt. % to 0.60 wt. % copper; 0.2. to 0.6 wt. % manganese; 0.2 wt. % to 0.6 wt. % iron; 0.01 wt. % to 0.07 wt. % strontium, up to 1.5 wt. % zinc; and up to 0.15 wt. % titanium, based on the total weight of the aluminum alloy. The aluminum alloy can also include other elements, for example impurities, each in an amount up to 0.05 wt. % and in a total amount up to 0.15 wt. %, based on the total weight of the aluminum alloy.

According to another example embodiment, in addition to at least 80 wt. % aluminum, the aluminum alloy includes 9.5 to 11.5 wt. % silicon, 0.3 wt. % to 0.8 wt. % zinc, 0.1 to 0.6 wt. % magnesium, 0.20 wt. % to 0.90 wt. % copper, 0.2 wt. % to 0.5 wt. % manganese, 0.3 wt. % to 0.6 wt. % iron, 0.01 wt. % to 0.03 wt. % strontium, and 0.15 wt. % maximum titanium, based on the total weight of the aluminum alloy. The aluminum alloy can also include other elements, for example impurities, each in an amount of less than 0.05 wt. % and in a total amount of less than 0.15 wt. %, based on the total weight of the aluminum alloy.

The compositions of the aluminum alloys according to the first and second example embodiments is provided in Table 1 below.

TABLE 1

Other
Other

Si
Zn
Mg
Cu
Mn
Fe
Sr
Ti
Each
Total

Ex. 1 Aural 5M
6.0-8.0
1.0-2.0
0.05-0.30
<0.05
0.20-0.40
0.25
0.03-0.08

0.05
0.15

Ex. 2 Aural 5R
6.0-8.0
1.0-2.0
0.05-0.30
0.10-0.40
0.2-0.5
0.3-0.6
0.01-0.03
0.15
0.05
0.15

maximum

Ex. 3 Aural 2R
9.5-11.5
0.3-0.8
0.1-0.6
0.20-0.90
0.2-0.5
0.3-0.6
0.01-0.07
0.15
0.05
0.15

maximum

The aluminum alloy according to the example embodiments is often referred to as Aural 2R because it is preferably obtained, in part, from recycled aluminum, such as recycled road wheels. The energy required to produce the aluminum alloy is reduced by about 95% when the aluminum alloy is formed from recycled materials.

Another aspect of the invention provides the cast component 10 formed of the aluminum alloy, and a method of manufacturing the cast component 10 by melting and casting the melted aluminum alloy. The method of forming the cast component typically begins by melting the aluminum alloy. Any casting process used to form components, for example high pressure die casting, low pressure casting, or squeeze casting. In one example embodiment, the casting process is a die casting process, which typically includes forcing the molten aluminum alloy into an unheated die or mold cavity under pressure. The die is typically formed from hardened tool steel.

The aluminum alloy according to example embodiments, such as the Aural 2R alloys, has a high amount of recycled (secondary materials), and after casting experiences a heat treatment, solution (T4), forced air quench and then artificial age (T7 temper). Thus, the cast aluminum alloy has a yield strength of at least 100 to 120 MPa, ultimate tensile strength (UTS) of 200 to 210 MPa, and an elongation of 10% to 20%.

FIG. 4 discloses the composition of the aluminum alloy according to an example embodiment (Aural 2R) relative to a comparative aluminum alloy (Aural 2). The aluminum alloy according to example embodiments provides for exceptional mechanical properties, corrosion resistance, rivetability, and castability. FIGS. 5A and 5B illustrate the mechanical properties of the aluminum alloy according to an example embodiment (Aural 2R) relative to a comparative aluminum alloy (Aural 2). The yield strength, ultimate tensile strength, and elongation are tested using ASTM E8/E8M-21 (Standard Test Methods for Tension Testing of Metallic Materials). The composition of the comparative aluminum alloy (Aural 2) includes at least 80 wt. % aluminum, 9.5 to 11.5 wt. % silicon, 0.1 to 0.6 wt. % magnesium, 0.4 wt. % to 0.6 wt. % manganese, 0.25 wt. % max iron, and 0.01 wt. % to 0.25 wt. % strontium, based on the total weight of the aluminum alloy.

FIGS. 6A-6C illustrate the results of a rivetability test comparing the aluminum alloy of the example embodiment (Aural 2R) to the comparative aluminum alloy (Aural 2). The rivetability test included applying a self-piercing rivet to the example aluminum alloy (Aural 2R) and the comparative aluminum alloy (Aural 2). The self-piercing rivet is a single-step technique which includes using a semi-tubular rivet to clinch sheets of the aluminum alloy together. The sheets are clamped between a die and blankholder, and the rivet is driven into the sheets between a punch and a die. The rivet pierces the top sheet and the die shape causes the rivet to flare within the lower sheet to form a mechanical interlock. The die shape causes a button to form on the underside of the lower sheet. Preferably, the rivet tail does not pierce though the button.

Aural 2R composition exhibited good corrosion resistance when subjected to a salt spray test for 100 hours according to Intergranular Corrosion (IGC) ASTM G110 and Cyclic Corrosion SAE J2334.

The cast component 10 formed from the casting step can be, for example, a component for use in a vehicle. The molten aluminum is formed to a solid component having the shape of the mold, which can be a complex shape. Many different types of components can be formed by the casting process, for example, a structural, body-in-white, suspension, or chassis component. After the casting process, the method can include an optional heat treating process or other finishing processes. However, it has been found that a heat treatment process may not be necessary when the component is formed from the improved aluminum alloy, which would provide the advantage of reduced process time and costs.

Generally, it takes up to 95 percent less energy to recycle than to produce primary aluminum, which reduces the carbon footprint of the foundries. The aluminum alloys of the present invention which include high amounts of recycled material, known as Aural 2R (R=high amt of recycled material), will utilize both post-consumer recycled shredded road wheels as well as pre-consumer wrought stamping offal. Development of these green aluminum alloys, using secondary recycled aluminum for BIW and structural components, will allow for both less cost of raw material, and a lower carbon footprint while still meeting stringent automotive industry standards. The cast components formed of the aluminum alloys have good rivetability and castability.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the following claims.