Partial melting behaviors and thixoforming properties of cast and extruded Mg-5.15Y-3.75Gd-3.05Zn-0.75Zr alloys

Cast and extruded Mg-5.15Y-3.75Gd-3.05Zn-0.75Zr alloys were selected as starting materials in a series of reheating experiments and thixo-compression tests. Homogenous spherical semisolid slurries were obtained when the reheating temperature and isothermal holding time were 560 °C and 20 s, respectively. However, the different grain sizes and different distributions of eutectic compounds in the starting materials resulted in different morphologies of the semisolid slurries. An innovative model was established to explain the dependency of the semisolid slurry on the morphology of starting material. The thixoforming properties of the semisolid slurry were affected by the forming temperature, strain rate, and its morphology. The dependency of thixoforming properties on the stain rate and morphology of semisolid slurry decreased at higher forming temperature. When the extruded alloy was formed at 560 °C with a strain rate of 0.1/s, a sample with a smooth surface was formed by a lower forming load.