Enhanced mechanical properties of LPSOp/Mg composites using super high pressure treatment

Abstract

The super high pressure (SHP) technique was employed to fabricate the magnesium matrix composites (MMCs) reinforced with long-period stacking order structure powder (LPSOp) by cubic-anvil large-volume press with six rams. The LPSOp was optimized through high energy ball milling (HEBM) with a chemical composition of Mg₈₅Zn₆Y₉ (at%). The microstructure and mechanical properties of LPSOp/Mg composite was characterized by X-ray diffraction (XRD), scanning electron microscopy/transmission electron microscopy (SEM/EDS), transmission electron microscopy (TEM), microhardness and compressive tests. The microhardness of LPSOp exhibits a notable increase after HEBM, and the thermal stability of LPSOp is affirmed through elevated annealing. The SHPed LPSOp/Mg consists of Mg and LPSO phase. Upon annealing at 400 °C for 1 h, the LPSO phase precipitates from solid solution of Mg and W phase is also identified. The strength of composites by SHP treatment and subsequently annealing is significantly improved compared with the pure Mg without LPSOp, which demonstrates the maximum compression yield strength (CYS) of 250 MPa and ultimate compression strength (UCS) of 375 MPa with satisfactory ductility. The enhanced mechanical properties are attributed to the synergistic reinforcement effects of the dispersed and 3D skeletal structure of LPSOp with excellent interfacial bonding, the coexistence of nano-scale LPSO and W phase and partial solid solution strengthening.