Effect of Pre-straining and Subsequent Annealing on Microstructure and Mechanical Property of Zr–Sn–Nb–Fe Zirconium Alloy

Abstract

Zirconium alloy is extensively used in nuclear industries as cladding and core structural material. However, the formability and service behavior are affected due to the anisotropy of mechanical property, which is detrimental to the specific application. In this work, effect of pre-straining and subsequent annealing (PA) on microstructure and mechanical property of Zr–Sn–Nb–Fe zirconium alloy is determined by means of scanning electron microscope equipped with electron backscatters diffraction and digital image correlation technique. It is found that the basal texture intensity and grain size of as-received sample decreases after pre-straining, the work-hardening value (n) increases from 0.126 of as-received sample to 0.152 of PA samples, while the anisotropy of mechanical property decreases gradually with the increase of pre-straining level. In addition, the strength, ductility and work-hardening value (n) of the PA samples tend to be accordant in the transverse direction, rolling direction (RD) and the 45° direction when the pre-straining level reaches 8%. The basal texture is gradually weakened and dispersed along the RD after annealing, whose orientation is favorable for the activation of pyramidal 〈c + a〉 slip to accommodate to the strain in thickness direction, which leads to the lower anisotropy (featured by the r-value). The low r-value and high work-hardening value (n) are favorable for improving formability. Hence, microstructure and texture of zirconium alloy can be modified though appropriate PA process to improve the comprehensive properties.