Research on Microstructures and Mechanical Properties of Mg-Gd-Y-Sr-Zr Alloy

Abstract

The microstructures and mechanical properties of Mg-Gd-Y-Sr-Zr alloy was investigated by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and tensile tests. The as-cast alloy contains a microstructure consisting of α-Mg matrix, Mg5Gd phase, Mg24Y5 phase and Mg17Sr2. As the temperature increases, the tensile strength of the alloy decreases. However, the elongation increases with increasing the temperature. Mg-30Gd (wt.%), Mg-25Y (wt.%), Mg-20Sr (wt.% ) and Mg-25Zr (wt. %) master alloys were made first by melting high purity Mg (N99.95%), Gd (N99.9%) and Y (N99.9%) in a vacuum medium- frequency induction furnace under an argon atmosphere. Then, the Mg-5Gd-3Y-2Sr-0.5Zr alloy ingots were prepared from high purity Mg (99.95%), the Mg-30Gd (wt.%), Mg-25Y (wt.%), Mg-20Sr (wt.% )and Mg-25Zr (wt.%) master alloys in a medium- frequency induction furnace with a graphite(99.99%) crucible under a mixed atmosphere of CO2 and SF6 with the ratio of 100:1. The chemical composition of the experimental alloys is listed Table 1. Table 1. Chemical composition of alloys (mass fraction, %)