Patent ID: 7214281
Filing Date: 2007-05-08
Classification: C22C,C22F

Abstract:
1. A method of producing an aluminum alloy extrusion product having improved fracture toughness, the method comprising the steps of: (a) providing a molten body of an aluminum base alloy comprised of 1.95 to 2.5 wt. % Cu, 1.95 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities; (b) casting said molten body of said aluminum base alloy to provide a solidified body, said molten aluminum base alloy being cast at a rate in the range of 1 to 6 inches per minute; (c) homogenizing said body by heating in a first temperature range of 840 to 860° F. followed by heating in a second temperature range of 860° to 880° F., the second homogenization temperature being greater than the first temperature to provide a homogenized body having a uniform distribution of η precipitate and zirconium containing dispersoids; (d) extruding said homogenized body to provide an extrusion, said extruding being carried out in a temperature range of 600° to 850° F. and at a rate sufficient to maintain at least 80% of the cross-sectional area of said extrusion in a non-recrystallized condition; (e) solution heat treating said extrusion; and (f) artificial aging said product to improve strength properties to provide an extrusion product having improved yield strength to fracture toughness ratio.