Anisotropy deformation behaviour of extruded Mg-2Zn-Al-0.2Ca-0.2Mn-0.2Gd (wt.%) bar with bimodal structure

Abstract

The anisotropy compression deformation behaviour of Mg-2Zn-Al-0.2Ca-0.2Mn-0.2Gd (wt.%) magnesium bar with bimodal structure were studied by compressing parallel and perpendicular to extrusion direction. EBSD technique was used to analyse the deformation behaviour, microstructure and texture evolution. The results show that Mg-2Zn-1Al-0.2Ca-0.2Mn-0.2Gd (wt.%) bar with special bimodal grain size but comparable texture characteristics with c-axes perpendicular to extrusion direction for both fine and coarse grains. The stress-strain curves and strain hardening rate response were significantly affected by the loading directions and initial texture. The anisotropy mechanical properties occurred due to different deformation behaviour. The dominant deformation mechanisms are basal slip in fine grains and extension twinning in coarse grains at initial deformation, however, the activation of prismatic slip and the unfavourable orientations for basal slip for sample compressing parallel extrusion direction contributes to the yield anisotropy. As the deformation continuing, twinning growth and basal slip dominant deformation. When loading perpendicular to extrusion direction, prismatic slip in fine grains also contributes to deformation to some extent. The c-axes of both samples turn to parallel to loading direction after compression.