Effect of Ca and RE (Y, Sm) on microstructure and mechanical properties of as-cast AZ91 magnesium alloy

Abstract

AZ91 magnesium as a lightest structural material, of the alloying additions to magnesium to date, composite Ca, Y and Sm have not been studied. Herein, the effects of Ca and RE(Y, SM) on the microstructure and mechanical properties of as-cast AZ91 magnesium alloy were studied. The results showed that the addition of 1 wt% Ca into AZ91 magnesium alloy could effectively refine the grains, and change the second phase distribution as well. Based on that, the addition of Y and Sm can change the second phase distribution of as-cast AZ91-1Ca alloy. When the content of Y and Sm increased to 0.67 wt% and 0.33 wt% respectively, Al2Y,Al2Sm and Al2(Yx, Sm1-x) composite phases are introduced to refine the alloy grains, also change the size and distribution of the second phase (Mg17Al12,Al2Ca). Furthermore the mechanical properties of AZ91 magnesium Alloy can be improved by Ca and RE (Y, Sm), among which the comprehensive mechanical properties of AZ91-1Ca-0.67Y-0.33Sm alloy has the best presentation, Consequently, the yield strength and tensile strength reached the highest, which are 126 MPa and 198 MPa respectively due to the ensuring elongation. The fracture mode of magnesium alloy can be changed by composite addition of Ca and RE (Y, Sm).