Formation process of AZ31B semi-solid microstructures through strain-induced melt activation method

A semi-solid microstructure of AZ31B magnesium alloy containing spherical solid particles was studied. This material was subjected to a series of spheroidizing treatments for various holding times at 863–893 K after being compressed by 28–30% in length at 573 K. The effects of heating temperature and holding time on microstructures were studied and the surface composition and line scans of the samples were investigated by energy-dispersive X-ray spectroscopy. It was found that increasing the heating temperature could accelerate the spheroidizing process, resulting in small spherical semi-solid microstructures. With a longer holding time, the solid content slightly changed and the solid particles became irregular. The concentrations of Al and Zn in the liquid phase were higher than those in the spheroidal solid phase and the peak intensity simultaneously changed. The macula observed through the microscope were thought to be possibly a Mn compound. Finally, the mechanism of formation of the semi-solid microstructure was discussed.