Strain hardening behavior of Mg–Y alloys after extrusion process

Abstract

The strain hardening is an effective mode of enhancing mechanical properties in alloys. In this work, the strain hardening behaviors of Mg-xY (x = 1, 2, and 3 wt%) after extrusion process was investigated using uniaxial tensile tests. Results suggest that the Mg–xY alloys are composed of α-Mg with a little amount of Mg24Y5 phase. The average grain size reduces from 19.8 µm to 12.2 µm as the Y content adds from 1 wt% to 2 wt%. Nevertheless, when Y content reaches 3 wt%, the grain size reaches to 12.9 µm, which is close to that of Mg–2Y. The strain hardening rate decreases from 883 MPa to 798 MPa at (σ–σ0.2) = 40 MPa, and Mg–2Y and Mg–3Y have the similar strain hardening response. Moreover, Mg–1Y shows an obvious ascending stage after the steep decreasing stage, which is mainly caused by the activation of twinning. The strain hardening behavior of Mg–xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent (VPSC) model. The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture. Keywords: Mg‒Y alloy, Strain hardening, Texture, Twinning, VPSC