Patent ID: 6645321
Filing Date: 2003-11-11
Classification: C22C

Abstract:
A method of casting an aluminum base alloy to provide a near net shape cast product having improved hot crack resistance in the as-cast condition, the method comprising:(a) providing a melt of an aluminum base alloy comprised of 2 to less than 3.5 wt. % Zn, 2.5 to 4 wt. % Mg, max. 2 wt. % total Fe and Mn in combination, max. 0.3 wt. % Si, max. 0.6 wt. % Cu, and optionally up to 0.5 wt. % Cr, the balance comprised of aluminum, incidental elements and impurities; (b) maintaining dissolved Ti in the range of about 0.005 to 0.1 wt. % in said melt to improve the resistance of said alloy to hot cracking; (c) adding a nucleating agent selected from the group consisting of metal carbides, aluminides and borides to said melt to provide an undissolved nucleating agent therein in the range of about 0.002 to 0.1 wt % for grain refining; and (d) solidifying said alloy to provide a near net shape cast product having a grain size of less than 125 microns and being free of hot cracks.