Thixoformability of a Mg–Gd–Y magnesium alloy and its mechanical properties

Abstract

A new magnesium alloy with composition of Mg–8·57Gd–3·72Y–0·54Zr (wt-, GW94) amenable to semisolid forming is presented. A quantitative investigation of its thixoformability in terms of metallurgical parameters in the semisolid state is performed based on Pandat thermodynamic calculation. The optimised working window for thixoforming is from 581 to 605°C, where the volume fraction of liquid does not change significantly with temperature. The alloy is then successfully thixoformed at 600°C, and a typical thixotropic microstructure is obtained. It is shown that significant improvement of mechanical properties is achieved in the thixoformed (TF) GW94 alloy compared to its permanent mould casting counterpart. This is attributed to an obvious decrease in the amount of porosity and fine distribution of the brittle Mg₂₄(Gd, Y)₅ particles in the thixoforming process.