Microstructure and Mechanical Properties of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr Alloy

Abstract: The microstructural evolution of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr (GWZK) alloy during homogenization and subsequent aging heat-treatment and the tensile properties of the peak-aged sample at various temperatures have been investigated. The phase transformation during homogenization, static precipitation during aging, and deformation mechanisms at 250 °C are systematically analyzed through XRD, TEM and EBSD measurements. The peak-aged GWZK alloy has good combination of strength and ductility at elevated temperatures owing to its high thermal stability by the LPSO phases distributed along the grain boundaries. The change (19 MPa) in the yield strength of peak-aged samples between RT and 250 °C is mainly related to easy gliding of dislocations on the non-basal planes due to the decrease in critical resolved shear stress of slip. Two strengthening models are applied to quantitatively describe the effect of { 11 2 - 0 } _α precipitate plates on Orowan strengthening corresponding to RT and 250 °C. Ignoring changes in solid solution strengthening and grain boundary strengthening of the peak-aged sample caused by increasing temperature, the calculated reduction value (16.5 MPa) in macroscopic yield strength from RT (based on the basal < a > slip mode) to 250 °C (based on the pyramidal < c + a > slip mode) is in good agreement with the measured reduction value (19 MPa). Graphic Abstract: [Figure not available: see fulltext.].