Inuence of Cooling Rate and Copper Content on the Microstructure of Zn- 27%Al Alloy under End-chill Casting

In this research, the effect of cooling rate and copper content on the microstructure of Zn–27%Al alloy was investigated using chilled casting in a sand mould. Microstructural examination showed that with decreasing cooling rate, dendrite arm spacing and the percentage of interdendritic phases increased. Moreover, addition of copper up to 1 wt. % did not lead to significant change in microstructure, while addition of 2, and 4 wt% copper led to the formation of -CuZn4 phase in the interdendritic regions. In addition, with decreasing cooling rate, the morphology of - precipitates varied from semi-plate-like to spherical.