Microstructural and textural evolution of commercially pure Zr sheet rolled at room and liquid nitrogen temperatures

A commercially pure Zr sheet with a typical bimodal basal texture was rolled up to 70% reductions at room temperature (RI) and liquid nitrogen temperature (LNT) to follow its microstructural and textural evolution. Various features developed during rolling were interpreted largely based on analyses on active deformation modes by the use of electron backscatter diffraction (EBSD) technique. Results show that only dislocation slip is activated during RI rolling while both slip and twinning occur in LNT-rolled specimens. There are always some non-deforming grains after RI rolling because their orientations with the c-axes close to the normal direction (ND) of the Zr sheet are unfavorable for slip. The LNT rolling allows these non-deforming grains to be deformed by [117 (2) over bar(2) over bar2} (1) over bar(1) over bar 23> compressive twinning and thus leads to more homogenous microstructures. The angle between basal pole peaks and the ND slightly decreases during RI rolling, which is attributed to the activity off {10 (1) over bar1}<11<(2)over bar>3> pyramidal slip. Many twins initiated at the early stage of LNT rolling could help retard the centralization of bimodal basal texture. In addition, calculations in light of key structural parameters measured by the EBSD reveal that the contribution from grain refinement induced by twinning makes the LNT-rolled specimens harder than the RI-rolled specimens. (C) (C) 2015 Elsevier Ltd. All lights reserved.