PREPARATION OF SUPER-PLASTIC ALUMINUM ALLOY

PURPOSE:To prepare a high strength super-plastic aluminum alloy having a fine grain structure, by applying heat treatment, hot processing and cold processing to an Al-Cu alloy ingot having a specific composition containing Mg, Si or the like in a combined form under a proper condition. CONSTITUTION:An Al-Cu alloy ingot, containing, on a wt. basis, 2-7% of Cu and further containing one or more of 2.5% or less Mg, 2% or less Si, 0.05- 0.5% Mn, 0.05-2.0% Cr, 0.05-0.5% Zr, 0.05-0.5% V and 0.15 or less Ti and comprising the remainder of Al and impurities, is subjected to homogenizing heat treatment at 400-550 deg.C and subsequently subjected to hot processing at 350-500 deg.C. In the next step, first heat holding is performed at 450-550 deg.C for 0.5-10hr and, subsequently, the hot processed one is cooled to a second heating temp. of 350-450 deg.C and held for 0.5-50hr. Thereafter, the processed one is cooled at a cooling speed of 30 deg.C/hr or more and subjected to cold processing under at least a draft of 30% or more to obtain a super-plastic aluminum alloy.