Study on microstructure evolution of deformed Mg-Gd-Y-Nd-Zr heat-resistant magnesium alloys after solid solution and ageing

The microstructure evolution of Mg-Gd-Y-Nd-Zr heat-resistant magnesium alloy after deformation and T5 or T6 treatment were studied. In thermoplastic deformation, dynamic recrystallization and dynamic precipitation has been taken place at the same time. The dynamic precipitation reduces the recrystallization nucleation driving force in the grain; it will prevent to occur dynamic recrystallization partially. Solid solution temperature was 530oC and hold 4h. Age hardening treatments were performed at 225oC and hold 16h. The alloy showed the comprehensive properties are obviously improved from T6 to T5 heat treatment. After T5 heat treatment the tensile strength of alloy increased to 359.3 MPa, increased by around 48.5%; Elongation is increasing from 5.17% to 6.5%. After peak ageing treatment, the main precipitation is β' phase, the precipitation phase have obvious pinning effect to grain boundary of the alloy, it will prevent the grain growth ageing for a long-time. At the same time, strengthening role of precipitate phase make its strength increased significantly