Aluminum alloy, method of casting aluminum alloy, and method of producing aluminum alloy product

Abstract

An aluminum alloy is composed of 15% or more and 7.5% or less by mass of silicon, 0.45% or more and 0.8% or less by mass of magnesium, 0.05% or more and 0.35% or less by mass of chromium, and aluminum, assuming that the total amount of the alloy is 100% by mass.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an aluminum alloy that has excellent castability, workability, and mechanical characteristics, a method of casting the aluminum alloy, and a method of producing a product of the aluminum alloy.[0003]2. Description of the Related Art[0004]Forged products of 6061 alloy aluminum, which has excellent strength and toughness and high corrosion resistance, are used for wheels, suspension arms and so on for weight reduction of vehicles. However, since the 6061 alloy has poor castability, near-net-shape blanks with complicated shapes are difficult to obtain and extrusion products are often used as blanks instead. Thus, the production cost tends to increase when parts with complicated shapes are produced. For this reason, casting aluminum alloys such as AC4C alloy and AC4CH alloy are used in some cases. When net-shape castings that are formed by casting such a casting aluminum alloy, or near-net-s...

AI Technical Summary

Benefits of technology

[0008]The present invention provides a novel aluminum alloy which has excellent castability and workability and has high mechanical characteristics. The present invention also provides a method of producing a casting that is formed from the aluminum alloy of the present invention and has high mechanical characteristics, and a method of producing an aluminum alloy product that has high mechanical characteristics which is obtained by machining the casting.

[0010]According to the above configuration, the aluminum alloy having the above composition has excellent castability and can be cast into a complicated net or near-net shape.

[0011]Also, since the Mg contained in an effective amount in the aluminum alloy contributes to grain refinement of eutectic Si, grain refinement of eutectic Si can be achieved without relying on the property improving elements such as Sr as described above. As grain refinement of eutectic Si can be achieved, the aluminum alloy exhibits high ductility and has excellent workability.

[0012]In addition, the strength of the aluminum alloy is improved when it contains an effective amount of Mg and contains Cr. Therefore, the aluminum alloy has improved strength and excellent corrosion resistance even if it is free from Cu.

[0018]A second aspect of the present invention relates to a casting method of an aluminum alloy. The casting method includes: pouring molten alloy comprising 3.5% or more and 7.5% or less by mass of silicon; 0.45% or more and 0.8% or less by mass of magnesium; 0.05% or more and 0.35% or less by mass of chromium; and aluminum; and allowing the molten alloy to cool and solidify.

[0023]According to the above configuration, an aluminum alloy casting and an aluminum alloy product having excellent castability and workability and having high mechanical characteristics can be obtained. In addition, when a solution heat treatment and an aging heat treatment are performed on the aluminum alloy casting or aluminum alloy product, spheroidization of eutectic Si is promoted and greater ductility develops, and the Mg is precipitated as magnesium silicide (Mg2Si) and mechanical strength such as tensile strength and proof strength improves.

Problems solved by technology

However, since the 6061 alloy has poor castability, near-net-shape blanks with complicated shapes are difficult to obtain and extrusion products are often used as blanks instead.

Thus, the production cost tends to increase when parts with complicated shapes are produced.

However, the above casting aluminum alloys have poor workability, compared to the 6061 alloy.

Thus, the mechanical characteristics, especially ductility, of an Al—Si based alloys always pose a challenge.

However, while these property improving elements are effective even when present in an extremely small amount, each element has a unique problem such as absorption of gas or reaction with fire-resistant materials.

Also, since the improving capacity decreases as the property improving elements are consumed with time after the addition, component management often cause trouble.

However, when Cu is added, Cu compounds may precipitate or crystallize and decrease the corrosion resistance of the Al—Si based alloys.

Especially, the addition of Cu tends to segregation in casting products and may impair the corrosion resistance thereof.

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