Microstructure evolution and mechanical properties of bimodal microstructure Mg-Gd-Y-Zn-Zr alloy under different heat treatment processes

In this work, the microstructure evolution and mechanical properties of a bimodal microstructure Mg-9.8Gd-3.6Y-2.2Zn-0.4Zr (wt.%) alloy under different heat treatment path was investigated to achieve a balance between strength and ductility. Results show that the static recrystallization behavior occurs during the solution treatment at 420-480°C. The recrystallization fraction and recrystallized grain size increase with increasing solution temperature and time. Simultaneously, static recrystallization promotes the expansion of [10-10]//ED basal fiber texture toward [11-20]//ED and [0001]//ED. β′ is precipitated on the prismatic planes of recrystallized grains after ageing of extruded alloys with bimodal microstructure, and a closed volume consisting of β′ and γ'/γ'' precipitates is presented in the unrecrystallized grains. The denser β′ precipitates are precipitated on the prismatic planes in recrystallized grains ageing after solution treatment. The bimodal microstructure and the precipitation behavior within different grains were modulated by different heat treatment paths to achieve a balance between strength and ductility.