Importance of basal slip on the plastic deformation behavior of zirconium alloy Zr702

Abstract

The plastic deformation behavior of a rolled Zr702 zirconium plate is investigated experimentally and with visco-plastic self-consistent (VPSC) simulations. Compression tests along the RD, TD and ND (rolling, transverse and normal directions, respectively) are done at room temperature and the plastic anisotropy (r-values or Lankford coefficients) is measured. EBSD measurements are used to assess the initial texture and the twin volume fraction after 10 % strain compression. Compression stress-strain curves are used to fit the critical resolved shear stress (CRSS) for prismatic, basal and 〈c + a〉 slip, and the CRSS for {10–12} tension twinning is fitted to reproduce the measured twin volume fraction. We found that basal slip is necessary to reproduce the plastic flow anisotropy, but stress strain curves can be reproduced with several sets of material parameters. Two set of material parameters are presented: first with the CRSS for basal slip equal to the CRSS for pyramidal 〈c + a〉 slip, second with the CRSS for basal slip half that for 〈c + a〉 slip. The predicted plastic strain anisotropy (r-value) strongly depends on the CRSS for basal slip. Simulations proved that the predicted r-values match the experimental ones only when the CRSS for basal slip is half that of 〈c + a〉 slip. Another self-consistent model is used to confirm that the CRSS for basal slip is half that of 〈c + a〉 slip. Slip traces analysis confirmed the activation of basal slip and pyramidal 〈c + a〉 slip, and pyramidal 〈a〉 slip was possibly activated. The different material parameters are used to predict the texture after plane strain deformation and simulations show that the textures are quite similar.