Method and process of non-isothermal aging for aluminum alloys

Abstract

An improved non-isothermal aging process for aluminum alloys is disclosed. The non-isothermal aging process enhances the aging process for 7000 series aluminum alloys. In particular embodiments, the process involves continuous heating increasing at a linear rate of about 25° F. for about 11 hours and maintains high strength and corrosion properties. In an exemplary embodiment, a 7085 aluminum alloy containing 6 to 10 wt. % zinc; 1.2 to 1.9 wt. % magnesium; 1.2 to 2.2 wt. % copper, with magnesium begin less than of equal to the weight % of copper plus 0.3%; and 0.05 to 0.4 wt. % zirconium, the balance aluminum, incidental elements and impurities is aged.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is based on and claims the benefit of U.S. Provisional application Ser. No. 60 / 781,811, filed Mar. 13, 2006.BACKGROUND [0002] 1. Field [0003] The present disclosure relates to non-isothermal heat treatments of aluminum alloys. More particularly, an improved aging process is disclosed for an aluminum alloy utilizing non-isothermal aging via linear heating. [0004] 2. General Background [0005] Precipitation hardenable alloys [0006] Typically, aluminum which have been heat treated and quenched are then subjected to an aging process to enhance the certain physical properties, including tensile properties. Previously, all precipitation hardenable aluminum alloys have been aged utilizing isothermal aging methods, through either single or multistage treatments. [0007] 7000 series aluminum alloys, which generally contain zinc, magnesium and copper, are used in a variety of applications due to its high strength in comparison to o...

AI Technical Summary

Benefits of technology

[0013] In particular embodiments, the 7000 series aluminum alloys are aged utilizing the non-isothermal aging process. By utilizing a non-isothermal linear heating rate, a per-aging step is eliminated aging time is drastically reduced. As a result, decreased costs are associated and become viable for more applications. For example, mold block applications are economically viable using this method.

Problems solved by technology

These particles coarsen as averaging continues, causing them to become incoherent with the matrix.

Current commercial aging practices of 7000-T7X alloys (T7X indicates overaged condition) include a pre-aging step at temperatures in the range of 225° F. to 250° F. This duplex aging practice is employed because aging performed directly above 300° F. results in the dissolution of GP Zones, which creates large precipitate-free zones and favors precipitation on dislocations and grain boundaries, both of which result in lower yield strength.

The traditional aging process require long aging times and utilize high amounts of energy, increasing costs.

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