Process optimisation for a squeeze cast magnesium alloy

The paper reports the influence of key process variables on zirconium-free (RZ5DF) and zirconium-containing (RZ5) magnesium–zinc–rare earths alloys by examination of the microstructure and mechanical properties of specimens produced by squeeze casting. Applied pressures from 0.1 to 120 MPa were considered and it was established that an applied pressure greater than 40 MPa was required to suppress the formation of microporosity. Increasing the applied pressure from 0.1 to 60 MPa, produced a reduction in cell size from 127 to 21 μm. The metal pouring and die temperatures considered in the investigation were within the range of 720–780 and 225–275 °C, respectively. It was established that the intermediate die temperature of 250 °C produced the highest tensile properties and that the presence of zirconium did not improve the as-cast properties of the squeeze cast alloy. The highest UTS value obtained for the zirconium-free RZ5DF alloy was 198 MPa compared to 195 MPa for the ZR5 alloy. These UTS value were approximately 50% higher than those for material cast under atmospheric pressure.