Microstructure evolution and mechanical properties of high performance Mg–10Gd–2Y–0·5Zn–0·3Zr alloy during heat treatments

Abstract

The microstructure evolution and mechanical properties of as cast Mg–10Gd–2Y–0·5Zn–0·3Zr during heat treatments were investigated in the present study. The appropriate solution treatment temperature of 530°C for the alloy was identified. The peak tensile yield strength of 202 MPa and elongation of 4·5% are obtained in the alloy aged at 200°C for 80 h. The high strength of the peak aged alloy is mainly ascribed to the dense precipitation of 14H type long period stacking ordered phase and β′ in the matrix during aging process. The different strengthening sources are reasonably evaluated by some conventional strengthening models. In the solution treated alloy, the solid solution strengthening is the main strengthening source to the total tensile yield strength. Nevertheless, the precipitation strengthening is the largest contributor (∼55%) to the tensile yield strength of the peak aged alloy also due to the strong strengthening effect of β′ and long period stacking ordered phase. The age hardening response of the cast T6 alloy is compared with that of the forged alloy. Results show that the combined effects of strengthening sources such as microstructure refinement by plastic deformation and precipitation strengthening during aging process are the optimal strengthening method of the present alloy.