Study on microstructure and mechanical properties of as-cast Mg-Zn-Sn-xCu(x=0,0.5,1.0,1.5wt.%) alloys

Abstract

In this paper, with the help of optical microscope, X-ray diffraction, scanning electron microscope and mechanical testing machine, the microstructures of ZT63-xCu (x=0,0.5,1.0,1.5wt.%) magnesium alloys were investigated and their mechanical properties were explored. It was found that the structure of as-cast alloys presented a typical dendrite morphology. The eutectic structure was refined by the addition of a certain amount of Cu, When Cu content continued to increase, the volume fraction of the eutectic structure increased and its continuity enhanced. The alloy without Cu addition was composed of α -Mg, MgZn2 and Mg2Sn phases. With the addition of Cu elements, MgZnCu phase was formed in the alloy, in addition to α-Mg, MgZn2 and Mg2Sn phases. With the increase of Cu content, the volume fraction of MgZnCu phase increased, and the proportion of MgZn2 phase gradually decreased. ZT63 alloy had the best matching of mechanical properties, its tensile strength and yield strength were 231Mpa and 80Mpa respectively, and the elongation reached 14.5%. With the increase of Cu, the mechanical properties of the alloys declined. When the Cu content is 1.5wt.%, tensile strength of the alloy decreased to 174Mpa, and the elongation was only 7%. The reduction of mechanical properties was related to the increase of MgZnCu phase.