Tailoring Precipitates in Mg-6Zn-2Gd Based Alloy Subjected to High Pressure Torsion

The precipitates formed at lower ageing temperatures are very unstable at higher application temperatures, thus are not ideal for the high temperature applications. A traditional approach in solving the problem is from alloy design and development route by increasing solute concentrations or addition of micro-alloying elements. Recently, high pressure torsion was also employed to tailor the precipitate microstructures of the age-hardening alloy that are significantly different from those obtained by conventional isothermal ageing treatments. In this contribution, an Mg-6Zn-2Gd-0.4Zr (wt. %) alloy has been subjected to high pressure torsion (HPT). The precipitate micro structure evolution during HPT processing has been characterised using TEM, with an aim to elucidate the effect of HPT processing on nucleation and growth of precipitates, and the mechanisms dominating the evolution of precipitate microstructure. This investigation demonstrates a new perspective for application of HPT to tailor precipitate microstructure for unique properties in service.