High strength aluminum casting alloy

Abstract

The present invention discloses a high strength Al—Zn—Mg—Cu (7000 series) alloy that can be cast, the cast alloy having a tensile strength of at least 500 megapascals (MPa) and 4% elongation. The cast alloy composition can include about 5.5-9.0 weight percent (wt. %) of zinc, 2.0-3.5 wt. % of magnesium, 0.1-0.5 wt. % scandium, 0.05-0.20 wt. % zirconium, 0.5-3.0 wt. % copper, 0.10-0.45 wt. % manganese, 0.01-0.35 wt. % iron, 0.01-0.20 wt. % silicon with a balance of aluminum and possible casting impurities. The alloy also has good fluidity comparable to high silicon cast aluminum alloys and components can be manufactured using direct chill casting, sand casting, and / or sand casting under high pressure.

Description

RELATED APPLICATION[0001]This application claims priority to U.S. Provisional Patent Application No. 61 / 392,310 filed on Oct. 12, 2010, having the same title and which is incorporated herein in its entirety by reference.FIELD OF THE INVENTION[0002]The present invention is related to an aluminum alloy, and in particular, to an aluminum casting alloy that exhibits high strength and adequate ductility.BACKGROUND OF THE INVENTION[0003]The use of aluminum alloys for lightweight components when compared to steel is known. For example, aluminum alloys are used extensively in the automotive and aircraft industry. In addition, with a face centered cubic structure, aluminum alloys have also found use in cryogenic type environments. For example, U.S. Pat. No. 7,060,139 filed on Nov. 8, 2002, titled “High Strength Aluminum Alloy Composition”, provides a high strength 7XXX series alloy that can be used at cryogenic temperatures and afford a tensile strength of at least 790 megapascals (MPa) with...

AI Technical Summary

Benefits of technology

[0006]A process for making the high strength aluminum cast alloy includes mixing and melting of aluminum and / or melting of an aluminum master alloy and providing alloying additions of zinc, magnesium, scandium, zirconium, copper, manganese, iron and / or silicon such that the above-described composition is provided. In addition, a melt of the alloy can be poured into a desired shape using any casting process known to those skilled in the art, illustratively including sand casting, investment casting, lost wax casting, and the like. The pouring temperature of the molten alloy should not be below 740° C. and a degassing step should be applied prior to pouring to remove dissolved gases (e.g. hydrogen) and solid inclusion from the melt. After the liquid alloy has been poured into the desired shape, it may or may not be allowed to solidify under atmospheric pressure. In some instances, the poured casting can be allowed to solidify under increased pressure, for example and for illustrative purposes only, 2 atmosphere, 5 atmosphere, 10 atmosphere, and the like. In addition, a cast component made from the cast aluminum alloy disclosed herein can be subjected to one or more heat treatment steps that afford improved mechanical properties thereof. For example, a heat treatment or temper for 7XXX series alloys known to those skilled in the art such as T1, T4, T6, T7 and the like can be performed on the cast component and provide improved mechanical properties when compared to a non-heat treated component. In addition, or in combination, heat treatment(s) that afford precipitation of coherent nano-particles of a Al3(Sc,Zr) phase can be performed to additionally improve mechanical properties.

Problems solved by technology

However, high strength 7XXX series alloys are known to be difficult to cast, with most common defects resulting from the casting thereof being intergranular porosity, hot tears, and cold cracks.

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