Direct Thermal Method of Aluminium 7075

Abstract

The evolution of microstructure affect from different pouring temperatures and holding times using a direct thermal method is presented in this paper. The direct thermal method is one of the thermal techniques which are used to produce semi-solid metal feedstock. In this experimental work, aluminium 7075 alloy was used. The experiments were carried out by processing a sample with a 0.7 °C/s cooling rate to evaluate the formation of the microstructure. In direct thermal method experiment, a molten 7075 was poured into a cylindrical copper mould at different pouring temperatures of 680 °C and 660 °C meanwhile the holding time of 20 s, 40 s and 60 s before quenched into room temperature water. The sample processed by the cooling rate of 0.7 °C/s produced a large microstructure. The formation of a spheroidal microstructure was obtained with the combination of a suitable pouring temperature and holding time. The pouring temperature of 665 °C and the holding time of 60 s produced a finer and uniform microstructure that is suitable for semi-solid feedstock.