HIGH STRENGTH ALUMINUM ALLOYS AND PROCESS FOR MAKING THE SAME

摘要

High strength aluminum alloys based on the Al-Zn-Mg-Cu alloy system preferably include high levels of zinc and copper to provide increased tensile strength without sacrificing toughness. In addition, small amounts of scandium are also preferably employed 5 to prevent recrystalization. Preferred ranges of the elements include by weight, 8.5-11.0% Zn, 1.8-2.4 % Mg, 1.8-2.6% Cu, 0.05-0.30% Sc and at least one element from the group Zr, V, or Hf not exceeding about 0.5%, the balance substantially aluminum and incidental impurities. During formation of the alloys, a homogenization process is preferably employed after alloy ingot casting in which a slow rate of temperature increase is employed as the alloy is heated as near as possible to its melting temperature. For the last 20-30F below the melting temperature, the rate of increase is limited to 20F/hr. or less to minimize the amount of low melting point eutectic phases and thereby further enhance fracture toughness of the alloy.