Effects of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy

In this study, the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated. The semi-solid slurry was produced by injecting fine gas bubbles into the melt through a rotating steel diffuser during solidification, and the samples of semi-solid slurry were taken by the rapid quenching method. The results show that fine and spherical α-Mg particles can be obtained under rotating gas bubble stirring treatment. The process parameters such as gas flow rate, cooling rate and rotation speed have significant influence on the morphology of primary solid particles. After rotating gas bubble stirring treatment, the higher the particle density, the finer and rounder the primary α-Mg particles. The formation of numerous solid particles is due to the combination mechanisms of copious nucleation and dendrite fragmentation.