Study on microstructure, mechanical and tribological properties of as-cast LPSO-containing Mg96Zn2Y2 matrix composite reinforced with TiB2 nanoparticles

In this work, the influence of TiB2 nanoparticles on microstructure, mechanical properties and tribological properties in the as-cast Mg96Zn2Y2 matrix composites containing 18R-LPSO (long-periodic stacking ordered) structure was investigated. Nano-TiB2/Mg96Zn2Y2 composites were fabricated by the combined process of powder mixtures compact extrusion and semi-solid stir casting. The results show that the appropriate TiB2 nanoparticles can significantly refine the microstructure, facilitate the precipitation of 18R-LPSO phase and optimize the growth pattern of 18R-LPSO and W phase. Meanwhile, the as-cast 1.5 wt%TiB2/Mg96Zn2Y2 composite with ultimate tensile strength (UTS) and elongation of 309 MPa and 16.2% exhibited better mechanical properties than that of matrix alloy with UTS and elongation of 175 MPa and 4.9%. In addition to traditional composites strengthening mechanisms, the synergistic strengthening effect (between TiB2 nanoparticles and 18R-LPSO phase) and the optimized growth pattern were also responsible for the excellent mechanical properties. Besides, the wear resistance of as-cast TiB2/Mg96Zn2Y2 composite is significantly improved under 5 N loading for 30 min, which was related to the enhanced hardness, work hardening ability and strength.