Grain refinement in laser remelted Mg-3Nd-1Gd-0.5Zr alloy

摘要： Columnar grains are normally favoured with the high cooling rate and steep thermal gradient in laser-based additive manufacturing. Here, we demonstrate that ?ne, fully equiaxed grains can be achieved in Mg-3Nd-1Gd-0.5Zr (EV31) alloy by laser surface remelting. The grains in the melt pool are remarkably re?ned from 74 μm to 3.5 μm, which can be attributed to the growth restriction effect, i.e. the constitutional supercooling formed by Zr solute during solidi?cation in combination with the high cooling rate imposed by laser surface remelting. This novel ?nding could be applied for the control of grain morphology and alloy design for additive manufacturing applications.