Effects of Y on Microstructure and Mechanical Properties of Variable-Cavity Liquid Forging Mg–Zn–Y–Zr Alloy

According to the experimental results and analysis, the effect of Y on the microstructure and mechanical properties of Mg–Zn–xY–Zr (x = 0, 1, 2, 3 and 4% wt%) magnesium alloy formed by variable-cavity liquid forging technology was studied. The results show that the microstructure changes obviously during deformation. The dendrites were elongated along the deformation direction after deformation. The content of Y has greatly influence on the kind and amount of second phase. With the content of Y increases from 0 to 4% (wt%), the changing process of main second phase is MgZn2–Mg3YZn6–Mg3Y2Zn3–Mg12YZn, and the content of precipitation gradually increases from 5.3 to 22.32% (vol%). Most of second phases have been broken to fine particles during variable-cavity liquid forging process. The influence of different fragmentized second phases is different. There is little microcrack generated in I and Z phase during variable-cavity liquid forging deformation, and the fragmentized particles of second phase can greatly improve the mechanical properties. W phase generates a mass of microcracks during deformation and has adverse implications to the part. The precipitates and grain size have significant effects on the mechanical properties of the alloy. The maximum tensile strength is 351.5 MPa, and the best elongation is 5.71%.