Microstructural Evolution of Semi-Solid AZ61 Magnesium Alloy during Reheating Process

AZ31 magnesium semisolid billets were prepared by a self-designed wavelike vibration sloping plate device,and an ideal globular or near-globular microstructure can be obtained by wavelike vibration sloping plate technique.The results show that,with the increase of reheating temperature and the prolongation of holding time,the liquid fraction in semisolid microstructure increases,and the solid phase grows gradually and spheroidises.The reheating microstructures at 580 ℃ and 610 ℃ are not suitable for thixoforming.The optimum reheating process parameters suitable for thixoforming are 590 ℃ for 40-60min or 600 ℃ for 30 min,under which the average grain diameter is 58-61 μm and solid fraction is about 87%.The lattice diffusion resulting in the variation of grain size is the dominant atomic diffusion mechanism of reheating.The solid-liquid interfacial tension results in the variation of globular or near-globular shape.