Grain refining mechanism of ZnO particles on magnesium alloys

Abstract

Grain refining of ZnO particles on magnesium alloys has been investigated by suction casting. Based on the experimental and thermodynamic data available, ZnO particles would be converted into the solute Zn in Mg melt. However, the ZnO particles have a slightly stronger grain refining potency than Zn. The grain refining efficiency of ZnO particles is mainly attributed to the restricting effect of Zn solute and in situ produced MgO particles as potent nuclei. Meantime, the large amount of reaction heat may cause intensive micro convection and mass transfer to eliminate the solute accumulation between existed grains, which could improve the nucleation rate.