Strain hardening behavior of Mg-Y alloys after extrusion process

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 alpha-Mg with a little amount of Mg24Y5 phase. The average grain size reduces from 19.8 mu m to 12.2 mu m 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 mu m, which is close to that of Mg-2Y. The strain hardening rate decreases from 883 MPa to 798 MPa at (sigma -sigma(0.2)) = 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. (C) 2019 Published by Elsevier B.V. on behalf of Chongqing University.