Grain refinement of Mg-Al binary alloys inoculated by in-situ oxidation

Utilizing oxide inclusion to induce heterogeneous nucleation event is an available method to achieve grain refinement. In this study, Mg-Al binary alloys were refined by inoculation of in-situ oxidation process. Results show that MgO and MgAl2O4 phases are primary oxide products for Mg-xAl alloys inoculated by in-situ oxidation. For pure Mg and Mg-1Al alloy, MgO is the only oxide product. MgAl2O4 is another oxide product for Mg-xAl alloy as Al content increases to 3 wt.%. For Mg-3Al alloy, average grain size significantly decreases from 1135 to 237 mu m, with a high grain refining ratio of 79.1%. Both MgO and MgAl2O4 possess nucleating potency for alpha-Mg grain. MgAl2O4 exhibits a higher nucleating potency due to the lower misfit with alpha-Mg. The grain refinement of Mg-xAl alloys inoculated by in-situ oxidation process is attributed to heterogeneous nucleation events of alpha-Mg grains on MgO or MgAl2O4 particles. Key words: Mg-Al alloy; grain refinement; heterogeneous nucleation; MgO; MgAl2O4