Effects of Zn on Microstructure and Mechanical Property of Mg-6Al-2Nd-2Ca Alloy

Mg-6Al-2Nd-2Ca alloy and Mg-6Al-2Nd-2Ca-1.2Zn alloy were prepared by the gravity casting method in a permanent mould. The as-cast alloys were homogenized, hot extruded and thereafter tested and analyzed by OM, XRD, SEM, EDS, TEM and tensile test. Effect of Zn addition on the microstructure and mechanical properties of Mg-6Al-2Nd-2Ca alloy were analyzed. The experimental results show that the addition of Zn could refine grains, which mainly exists in the alpha-Mg matrix, reduce the solid solubility of Al in the alpha-Mg matrix and generate more Al-Nd phases. After homogenization treatment, the microstructure of the two alloys are more uniform, and the amount of precipitated phase is reduced compared with that of the as-cast alloys. After hot extrusion, the hard and brittle phases in the two alloys are crushed, the grains are refined, and the mechanical properties are obviously improved. The tensile strength, yield strength and elongation of the Mg-6Al-2Nd-2Ca-1.2Zn are 294.0 MPa, 197.1 MPa and 11.6%, respectively, which are attributed to the combination of refinement strengthening and second phase strengthening.