Preparation and rheo-squeeze casting of semi-solid AZ91–2 wt% Ca magnesium alloy by gas bubbling process

In this study, semi-solid slurry of AZ91–2 wt% Ca (AZ91–2Ca) alloy was prepared by gas bubbling and shaped by rheo-squeeze casting process. The results indicate that fine semi-solid slurry of AZ91–2Ca alloy could be obtained by gas bubbling within 30 s, with primary α-Mg particles having an average diameter less than 50 μm and average shape factor higher than 0.7. With the decrease of pouring temperature from 599 to 590 °C, both tensile strength and elongation of rheo-squeeze casting AZ91–2Ca alloy first increased and then decreased. The rheo-squeeze casting AZ91–2Ca alloy sample prepared at pouring temperature of 596 °C exhibited the peak tensile strength and elongation. Compared with conventional squeeze casting, the improvement in mechanical properties of rheo-squeeze casting AZ91–2Ca alloy was mainly attributed to the grain refinement strengthening, including the refinement and spheroidization of primary α-Mg particles and the refinement in the residual melt.