Effect of ECAP process on the activation of deformation mechanisms during subsequent uniaxial tension of Mg-ZEWK2000 sheets

Abstract

The present work investigates the influence of two different processing routes on mechanical behavior of Mg-Zn-Nd-Y-Zr (ZEWK2000) Mg sheets. Hot-rolled sheets, with dimensions of 200 × 200 × 1.8 mm3, were processed at 225 ℃ by a two equal channel angular pressing (ECAP) passes following the route DC2 with a rotation of 90° around the normal direction (ND) of the sheet. Shear deformation applied by ECAP weakens the texture and promotes a broad angular distribution of basal planes in the pressing direction. The resulting crystallographic texture promotes a change of the balance of active deformation mechanisms, i.e. slip of dislocations and twinning, during subsequent uniaxial deformation. To assess the effect of texture changes on the activation of slip systems, a systematic analysis of the slip traces after uniaxial tension of ECAP processed samples at room temperature was carried out. The analysis reveals the profuse activation of additional slip systems than the common basal  slip and pyramidal II , where non-basal slip such as prismatic  , pyramidal  and pyramidal I played a major role than expected in the rolled sheet. The relative activity of deformation mechanisms was significantly changed in the ECAP processed sheet, where extension twinning, basal , pyramidal I  and pyramidal II  slip dominated the deformation. Overall, the activation of extension twinning in the ECAP processed sheet is beneficial for the reduction of anisotropy and the improvement of formability of the processed samples.