Semi-solid powder moulding for preparing medical Mg–3Zn alloy, microstructure evolution and mechanical properties

Abstract

Medical Mg-based alloys are extensively applied because of its degradability, low elastic modulus, etc In this study, Mg–3Zn alloy was prepared by semi-solid powder moulding. Firstly, pure Mg powders with 3 wt% of pure Zn powders were mixed, and then the mixture were compressed into a designed mould at 540, 560, 580, 600, and 620 °C, respectively. The results show that as the temperature increases, relative density, the compressive strength and microhardness increase firstly and then decrease when the temperature reaches to 620 °C. The highest relative density, microhardness and compressive strength is 97.4%, 125 HV, 315.4 MPa, respectively at the forming temperature of 600 °C. The microstructure is mainly composed of α-Mg with a little of intermetallic phases (MgZn2, Mg4Zn7 and Mg51Zn20), the grain morphology is equiaxed grain with the size of about ∼30 μm. When prepared at a low temperature, the main combination mechanism of powders is hot rolling densification. Flowing and filling of liquid is the main combination mechanism at high temperature. Broken-up of particles and deformation including viscoplastic deformation contribute to the densification. More Mg was dissolved into Zn as the temperature increases, and the liquid fraction is mainly influenced by the dissolved Mg content. The sample prepared at 600 °C has a lowest corrosion rate (0.09 mm/year), which proves that semi-solid powder moulding is a promising method to prepare medical Mg-based alloys.