Pre-deformation enhanced {10-12} twinning in a zirconium alloy

Twinning is an important plastic deformation mode for zirconium (Zr) and its alloys. In this work, pre-compression followed by orthogonal re-compression, was performed to investigate the effect of pre-deformation on the nucleation of twinning in a textured Zr702 alloy sheet. Microstructures and texture evolution during deformation were examined by electron backscatter diffraction (EBSD) method. It is found that the pre-compression along the normal direction (ND) enhances the activation of {10-12} tensile twins during re-compression along the rolling direction (RD) compared with that in single-step compression along the RD. Moreover, the {10-12} twins preferentially nucleate at grain boundary with relative low misorientation angle (10-30 degrees). When re-compression along the transverse direction (TD) after pre-compression along the ND, the twinning behavior is different from that in re-compression along the RD, which may be attributed to different deformation mechanisms when re-compression along the TD and the RD.