Role of C and Fe in Grain Refinement of an AZ63B Magnesium Alloy by Al-C Master Alloy

In this study, grain refining effect of Al-1.5C master alloy was examined on an AZ63B magnesium alloy, and the refining mechanism was studied through investigating the role of C and Fe in this process. The results show that addition of Al-1.5C master alloy leads to significant decrease of the mean grain size from about 270 μm to 50 μm at the center of the AZ63 alloy ingot. Grain refinement by carbon addition is mainly due to the heterogeneity nucleation on the Al-, C-, O-, Fe- and Mn-rich particles, but not constitutional undercooling caused by the carbon solute element. Fe plays an important role in the formation of the nucleating particles, but not acts as an inhibiting element.