On grain coarsening and refining of the Mg-3Al alloy by Sm

摘要

The effect of Sm on the microstructure of a Mg-3Al alloy has been investigated where it was found that the size of the primary alpha-Mg grains was significantly coarsened by the addition of 0.7 wt. % Sm, but dramatically refined by 2.1 wt. % Sm. It is proposed that the coarsening effect of Sm is due to a decrease in the nucleation potency of the native Al-Fe-C-O particles when they transform to the lower potency Al-Fe-Sm-C-O particles. The grain refinement observed when 2.1 wt. % Sm is added, is caused by the formation of potent Al2Sm nucleant particles prior to the solidification of alpha-Mg. The "Interdependence Theory" was then applied to describe the nucleant selection process in the Mg-3Al-2.1Sm alloy. (C) 2015 Elsevier B.V. All rights reserved.