Effect of Homogenization Treatment on Microstructure and Properties of ZnAl15 Alloy

Abstract

The microstructure, microhardness and corrosion resistance of as-cast and as-annealed ZnAl15 alloys were investigated by OM, SEM, EDX and DSC techniques. It was found that microstructure of as-cast ZnAl15 alloy was primary dendrites and eutectic matrix. But Primary discontinuous precipitation of αs and βs phase occurred at room temperature. During homogenization treatment, discontinuous precipitation of αs and βs phase occurred completely and accompanied with emitting heat. The final microstructures of decomposed αs and βs phase in primary dendrites were fine and coarse lamellar structures respectively. The final microstructures of decomposed βs, which located at the edges of the αs phases or in eutectic matrix were that α phase distributed in η matrix. The microhardness of both primary dendrites and eutectic matrix in ZnAl15 alloys decreased after homogenization treatment due to the decomposition of supersaturated solid solutions. The result of accelerated corrosion test showed that homogenization treatment has a certain beneficial effect on the corrosion resistance of ZnAl15 alloy.