Microstructure and mechanical properties of as-cast Mg-8Li-xZn-yGd (x=1, 2, 3, 4; y=1, 2) alloys
(1. National Engineering Research Center of Light Alloy Net Forming and Key State Laboratory of Metal Matrix Composite, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2. Shanghai Innovation Institute for Materials, Shanghai 200444, China;
3. Shanghai Spaceflight Precision Machinery Institute, Shanghai 201600, China;
4. Shanghai Engineering Technology Research Center of Near-Net-Shape Forming for Metallic Materials, Shanghai 201600, China)
2. Shanghai Innovation Institute for Materials, Shanghai 200444, China;
3. Shanghai Spaceflight Precision Machinery Institute, Shanghai 201600, China;
4. Shanghai Engineering Technology Research Center of Near-Net-Shape Forming for Metallic Materials, Shanghai 201600, China)
Abstract: The as-cast Mg-8Li-xZn-yGd (x=1, 2, 3, 4; y=1, 2; wt.%) alloys were prepared in a vacuum induction furnace and their microstructure and mechanical properties were investigated. The results show that the increase of Zn content results in the volume fraction of W-phase (Mg3Zn3Gd2) increasing while that of Mg3Gd phase decreasing. The strength of Mg-8Li-xZn-1Gd alloys is improved with the increase of Zn content, which is ascribed to the second phase strengthening of fine strip-like W-phase and the solid solution strengthening of Zn element. For Mg-8Li-4Zn-yGd alloys, the increase of Gd content leads to the appearance of coarse and discontinuous net-like W-phase, which decreases the strength. The Mg-8Li-4Zn-1Gd alloy exhibits an optimum comprehensive performance with the yield strength, ultimate tensile strength and elongation of 154.7 MPa, 197.0 MPa and 12.4%, respectively. In addition, the aging behavior of the typical alloys was also investigated.
Key words: Mg-Li-Zn-Gd alloy; W-phase; microstructure; mechanical properties; aging behavior