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.

Graphic Abstract

中文翻译：

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预应变及后续退火对Zr-Sn-Nb-Fe锆合金组织和力学性能的影响

摘要

锆合金被广泛用于核工业中作为包层和核心结构材料。但是，由于机械性能的各向异性而影响可成形性和使用性能，这不利于特定的应用。在这项工作中，通过配备电子背散射衍射和数字图像相关技术的扫描电子显微镜，确定了预应变和随后的退火（PA）对Zr-Sn-Nb-Fe锆合金的组织和力学性能的影响。结果发现，经过预应变后，样品的基础织构强度和晶粒尺寸减小，加工硬化值（n）从原样的0.126增加到PA的0.152，而力学性能的各向异性随预应变水平的增加而逐渐降低。另外，当预应变水平达到8％时，PA样品的强度，延展性和加工硬化值（n）在横向，轧制方向（RD）和45°方向上趋于一致。退火后，基底织构逐渐沿RD减弱并分散，其取向有利于激活金字塔形<c + a>滑移，以适应厚度方向的应变，从而导致较低的各向异性（以r-为特征）值）。低r值和高加工硬化值（n）有利于改善可成形性。因此，可以通过适当的PA工艺改变锆合金的组织和织构，以提高综合性能。

图形摘要