Microstructure and tensile property characterization of a nickel-containing zinc-based alloy: effects of heat treatment and test conditions

This study analyzes the effects produced by heat treatment on the microstructural features, electrical conductivity, hardness and tensile strength, and elongation of a nickel-containing zinc-based alloy. The influences of test temperature and strain rate on the tensile properties of the alloy have also been studied. The as-cast alloy showed primary α dendrites surrounded by eutectoid α+η and ε. Heat treatment led to breaking of the dendritic structure and generation of microconstituents with improved uniformity of distribution. The nickel-containing phase was also observed in as-cast as well as heat-treated conditions. Heat treatment had negligible influence on the morphology of the nickel-containing phase. Tensile properties improved with strain rate. Increasing temperature caused the tensile strength to reduce, while elongation was affected in an opposite manner. Heat-treated specimens attained less tensile strength and hardness but improved elongation as compared with the as-cast alloy. The observed response of the alloy has been explained on the basis of specific features of its various microconstituents and substantiated with its fractographic features and subsurface characteristics.