Microstructure of superplastic alloys

Abstract

Abstract The mode of decomposition of a eutectoid Zn–Al alloy has been related to the superplastic properties of the alloy. Decomposition during slow quenches or at high transformation temperatures produces a typical lamellar eutectoid structure with conventional mechanical properties. Decomposition at room temperature after a rapid quench produces a fine (∼ 1 μ) mixture of equiaxed zinc-rich and aluminium-rich grains and the alloy then shows tensile elongations of > 1000% at a deformation temperature of 250°C. It is proposed that the equiaxed structure is produced by spinodal decomposition.