Improving microstructure and mechanical properties of hypoeutectic Al-Mg2Si alloy by Gd addition

The effect of Gd element on the microstructure and tensile properties of a hypoeutectic Al-Mg2Si alloy, i.e. AlMg5Si2Mn alloy, was systematically studied. The results show that Gd can refine the primary alpha-Al phase and modify the eutectic Mg2Si phase in the Mg2Si reinforced Al alloy. With Gd addition, the morphology of the primary alpha-Al phase is varied from coarse dendrite to small round particle. Meanwhile, the morphology of the eutectic Mg2Si phase can change from mazelike thick lamellar to thin coralline fiber. The yield strength, ultimate tensile strength and the ductility are remarkably enhanced. It is proposed that the refinement of primary alpha-Al phase results from the formation of Al3Gd, and the modification of eutectic Mg2Si phase is attributed to the Gd segregation and composition supercooling in front of the growing Mg2Si phase. (C) 2019 Elsevier B.V. All rights reserved.