Schmid Factor Maps for Predicting Slip and Twinning Behaviors in Zirconium

A series of Schmid factor (SF) maps for different slip and twinning modes in zirconium were calculated and illustrated as a function of the tensile angle between the applied stress and the c-axis together with the projective angle on the basal plane. The results show that the deformation modes include three groups of slip systems, i. e. basal slip, prismatic slip, pyramidal <a> and <c+a> slip, and four groups of twinning systems, i. e. {1012}, {1121}, {1122} and {1011}. The "soft" and "hard" orientation zones of individual plastic deformation modes were determined. A variant selection criterion for slip and twinning of zirconium was proposed. The plastic deformation mechanism was interpreted based on the Schmid factor maps in combination with the experimental data of the critical resolved shear stress (CRSS) under different deformation modes. The predicted plastic deformation mechanism is consistent with the experimental results.