Solid state recycling of Mg–Gd–Y–Zn–Zr alloy chips by isothermal sintering and equal channel angular pressing

Abstract

The Mg-7Gd-4Y-2Zn-0.5Zr alloy chips were successfully recycled through isothermal sintering and equal channel angular pressing (ECAP). The mechanical properties and microstructure evolution of samples during the recycling process were studied in detail. The eutectic phases in the as-cast alloy transform into long period-stacking ordered (LPSO) phases after homogenization, which can improve the plasticity of the material. After isothermal sintering, the density of the sample is lower than that of the homogenized sample, and oxide films are formed adjacent to the bonding interface of the metal chips. Hence, the plasticity of the sintered sample is poor. Dense samples are fabricated after ECAP. Although the grains are not refined compared to the sintered sample, the microstructure becomes more uniform due to recrystallization. Fiber interdendritic LPSO phase and kinked 14H-LPSO phase are formed in the alloy due to the shear deformation during the ECAP process, which improves the strength and plasticity of the sample significantly. Furthermore, the basal texture is weakened due to the Bc route of the ECAP process, which can increase the Schmid factor of the basal slip system and improve the elongation of the sample. After 2 ECAP passes, the fully densified recycled billet shows superior mechanical properties with an ultimate tensile strength of 307.1 MPa and elongation of 11.1%.