Effect of pack-forging on microstructure and properties of Mg-Gd-Y-Zn-Zr alloy

An ultrahigh strength Mg-10Gd-4Y-1.5Zn-0.5Zr alloy was prepared by the combined process of extrusion, packforging and aging treatment. The resultant alloy possesses a bimodal grain structure, a high number density of nanoprecipitates and long period stacking ordered (LPSO)/stacking faults (SFs). Numerous dispersive precipitates formed after the aging treatment due to the high number density of dislocations induced by packforging at low forming temperatures. The additional compression stress benefited from the pack-forging accelerates the dynamic dissolution of the LPSO phase and precipitation of SFs. Heterogeneous deformation induced (HDI) strengthening is achieved from the bimodal grain structure and different types of dynamic recrystallization (DRXed) grains, which significantly enhance the yield strength. Besides, grain-boundary strengthening and precipitation strengthening contribute to the high yield strength as well.

Automated summary

The ultrahigh strength Mg-10Gd-4Y-1.5Zn-0.5Zr alloy is prepared through a combination of extrusion, packforging, and aging treatment, resulting in a bimodal grain structure, high number density of nanoprecipitates, and LPSO/SFs. The alloy's mechanical properties are further enhanced by the formation of bimodal grain structure and numerous dispersive precipitates during the processing, including the precipitation of SFs and dynamic dissolution of the LPSO phase.