A comparative study between AZ31 and Mg-Gd alloys after high-pressure torsion.

Abstract

The evolution of microstructure, texture, and mechanical properties of AZ31 (Mg-3Al-1Zn, wt.%) and Mg-0.6Gd (wt.%) alloys were investigated and compared after high-pressure torsion at room temperature through the equivalent strain range of εeq = 0.6-287.5. The results demonstrated that the grain refinement behavior is different for these two alloys. For the AZ31 alloy, dynamic recrystallization (DRX) was restricted leading to a gradual and continuous formation of ultrafine grains with a mean grain size of ~0.3 µm through the entire strain range and the development of deviated B, C1, and C2 texture fibers. For the Mg-0.6Gd alloy, the DRX was very fast and a rapid ultrafine grain microstructure with a mean grain size of ~0.7 µm was developed at a strain range of εeq = 0.6-5.7 and this remained stable with a relatively stable B-fiber over the strain range εeq = 5.7-287.5. The evolution of microhardness in the AZ31 alloy indicated a strain hardening without recovery while that of the Mg-0.6Gd alloy showed a strain hardening with recovery. The differences between the AZ31 and Mg-0.6Gd alloys are discussed based on a comprehensive characterization of twinning, dislocation density, the initial microstructure and the presence of second phases.