Evolution of the semi-solid microstructures of 7075 Aluminum alloy cast by LSC

The evolution of 7075 aluminum alloy's microstructures and the distribution of the main elements were studied when the billets made by LSC were reheated. The grains are bigger and more globular with the holding temperature increasing when the holding time is stable, also with the holding time increasing when the holding temperature is stable. The rosette-shaped and spheroidal grains can be turned into small and uniform global grains when the reheating temperature is about 580°C and the holding time is 15-30 min, or the reheating temperature is about 600°C and the holding time is 5-15 min. The grains average diameter is 40-55 μm which is suitable for thixoforming. The distribution of Mg is almost uniform, but Cu is seriously concentrated and Zn is slightly concentrated in the grain boundary after reheating. The mechanism of the evolution of the global grains from the as-cast microstructures was analyzed.