Microstructure and Mechanical Properties of Mg-Al-Zn Alloy Prepared by SPS Sintering–Extrusion Combined Forming

Abstract

To improve the poor plasticity and low absolute strength of magnesium alloy at room temperature, the Mg-Al-Zn (AZ91) magnesium alloy was prepared using spark plasma sintering (SPS)–extrusion combined forming, and the microstructure and mechanical properties were studied in depth. The results showed that the microstructure of the SPS-sintered AZ91 alloy was composed of equiaxed prior particles, and that the compactness of the microstructure was low. There were micropores and oxide layers at the prior particle boundaries. The average grain size was 6.42 μm, and the ultimate tensile strength (UTS) and elongation (El) were 165.3 ± 5.8 MPa and 2.4 ± 0.1%, respectively. After extrusion deformation, the equiaxed prior particles were elongated along the extrusion direction, showing a long strip shape, and the compactness of the microstructure was significantly improved. The precipitated phase and oxide layer continuously distributed at the sintering neck were broken and refined into fine particles, which were dispersed along the prior particle boundaries. The average grain size was 2.16 μm, and its UTS and El were 321.4 ± 2.4 MPa and 5.0 ± 0.3%, respectively. The improvement of the mechanical properties was mainly attributed to the combined effect of increased microstructure compactness, improved bonding strength between prior particles, grain refinement.