Microstructure and tribological behavior of Mg-Gd-Zn-Zr alloy with LPSO structure
(1. College of Mechanical Engineering, Shanghai University of Engineering Science, Shanghai 201600, China;
2. National Engineering Research Center of Light Alloy Net Forming,
Shanghai Jiao Tong University, Shanghai 200240, China;
3. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
2. National Engineering Research Center of Light Alloy Net Forming,
Shanghai Jiao Tong University, Shanghai 200240, China;
3. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: A Mg-14.28Gd-2.44Zn-0.54Zr (mass fraction, %) alloy was prepared by conventional ingot metallurgy (I/M). The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribological behaviors of the as-cast and solution-treated alloys were investigated under oil lubricant condition by pin-on-disc configuration. The wear loss and friction coefficients were measured at a load of 40 N and sliding speeds of 30-300 mm/s with a sliding distance of 5000 m at room temperature. The results show that the as-cast alloy is mainly composed of α-Mg solid solution, the lamellar 14H-type long period stacking ordered (LPSO) structure within matrix, and β-[(Mg,Zn)3Gd] phase. However, most of the β-phase transforms to X-phase with 14H-type LPSO structure after solution heat treatment at 773 K for 35 h (T4). The solution-treated alloy presents low wear-resistance, because the hard β-phase is converted into thermally-stable, ductile and soft X-Mg12GdZn phase with LPSO structure in the alloy.
Key words: Mg-Gd-Zn-Zr alloy; long period stacking ordered (LPSO) structure; microstructure; friction; wear