A PROCESS FOR THE PREPARATION OF ALUMINIUM-ZINC-MAGNESIUM-MAGANESE-ZIRCOMIUM-SILVER ALLOY HAVING IMPROVED STRESS CORROSION CRACKING RESISTANCE

摘要

(a) preparing a charge mixture of primary aluminium and Al-8.5 wt% Mn master alloy; (b) meltirg the said charge mixture, adding to this molten charge elemental paie Zn followed by raising the temperature of the molten charge as icrein described; (c) adding of AI 50 wt.% Mg master alloy, Mg-28 wt% 2r master alloy and Al-2 w% Sc master alloy in the above sequential xder to the above molten charge followed by super heating for a period of about 10 minutes; (d) adding nuclent pellets at reduced temperature for grain refinement; (e) degassing the molten melt to remove dissolved gases and pouring the molten rnelt under inert gas atmosphere, preferably argon atmosphere, into a pre-heated mould; (f) homogenizing, scalping arid rolling the sound billets into plates; (g) solution treating, quenching, and stretching the alloy sheets followed by two-step artificial aging wherein the Al-Zn Mg-Mn-Zr-Sc alloy comprising of AI- (4.8-5.3) Zn- (1.8-2.3) Mg-(0.2-0.4) Mn- (0.11-0.19) Zr-(0.10-0.30) Sc inw