Abstract
Various properties of the high-aluminum zinc-base alloys are susceptible to the mould conditions or cooling rate as a function of pouring temperature and preheating temperature of the chill mould. This paper describes the effects of cooling rate on various properties of the zinc-22% aluminum eutectoid alloy castings.
When the preheating temperature of the chill mould is elevated from room temperature to 350°C and the metals are poured at 550°C, the tensile strength and hardness fall but the elongation and impact strength rise. The latters contrary fall at the elevated teperature of the chill above 300°C. When the mould temperature is maintained at 100°C and the metals are poured at elevating temperature from 500 to 700°C, little difference is found in the various properties. Pouring at 550°C and preheating of the chill at 100 to 200°C ensure the optimum castings. These castings have relatively excellent properties and stability during aging. They are solidified in the freezing temperature range at the cooling rate 320 to 170°C/min.
