The microstructural evolution of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr (GWZK) alloy during homogenization and subsequentaging heat-treatment and the tensile properties of the peak-aged sample at various temperatures have been investigated. Thephase transformation during homogenization, static precipitation during aging, and deformation mechanisms at 250 °C aresystematically analyzed through XRD, TEM and EBSD measurements. The peak-aged GWZK alloy has good combinationof strength and ductility at elevated temperatures owing to its high thermal stability by the LPSO phases distributed alongthe grain boundaries. The change (19 MPa) in the yield strength of peak-aged samples between RT and 250 °C is mainlyrelated 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 efect of {11 −2 0}훼precipitate plates on Orowanstrengthening 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 macroscopicyield strength from RT (based on the basal
slip mode) to 250 °C (based on the pyramidalslip mode) is in goodagreement with the measured reduction value (19 MPa).