BigPatents India

This invention relates to a process for the preparation of Aluminium-Zinc-Magnesium-Copper-zirconium Silver (AI-Zn-Mg-Vu-Zr-Ag) alloy having improved weldability comprising steps of : (i) preparing a charge mixture of primary aluminium A1-30 wt% Cu master alloy and master alloy AI-30 wt%; (ii) melting the said charge mixture of primary aluminium Al-30 wt%, Cu master alloy and Al-9.8 wt%, Ag master alloy, adding to this molten charge elemental pure Zn, followed by raising the temperature of the molten charge as herein described; (iii) adding of AI-51 wt% Mg alloy, Mg-28 wt% Zr master alloy in the above sequential order to the said molten charge followed by super heating for a period of about 10 minutes; (iv) adding nucleant pellets at reduced temperature for grain refinement; (v) degassing the molten melt to remove dissolved gases and pouring the molten melt under inert gas atmosphere, preferably argon atmosphere, into a pre-heated mould; (vi homogenizing scalping and rolling the sound billets into sheets; (vii) solution treating, quenching, and stretching the alloy sheets followed by two-step artificial aging wherein the aluminium-zinc-magnesium-copper-zirconium-silver (AI-Zn-Mg-Cu-Zr-Ag) alloy comprising Al-(7.4-8.2) Zn-(1.6-2.1) Mg-(1.5-2.1) Cu-(0.11-0.19) Zr-(0.3-.08) Ag in wt%.