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为了探明a’’相U-5.8wt%Nb合金的晶格响应和变形特性,对力学拉伸加载下的合金变形行为进行了原位的X射线衍射(XRD)研究,获得了合金从弹性变形直至断裂的过程中晶格对外加应力的响应特征。实验中,每增加一定变形量就对试样进行原位的XRD分析,用单峰拟合法和Rietveld全谱精修方法处理数据,分析了合金变形过程中的晶格演化行为。结果显示,拉伸过程中,试样的晶胞参数、衍射峰强度和晶面间距都随外加应变有规律地变化。晶格响应分析结果表明,合金晶胞各方向弹性极限的显著差异是第一屈服平台形成的内在原因,该屈服平台的变形过程包括了孪生变形和弹性变形2种机制。利用研究结果能够很好地解释合金的形状记忆效应。
In order to investigate the lattice response and deformation characteristics of a-phase U-5.8wt% Nb alloy, in-situ X-ray diffraction (XRD) studies of alloy deformation under mechanical tensile loading were performed. Response of Lattice to External Stress during Deformation until Fracture. In the experiment, the XRD analysis of the sample was carried out in situ for each increment of deformation. The data were processed by single-peak fitting method and Rietveld complete spectrum refinement method, and the lattice evolution behavior during the deformation was analyzed. The results show that during the stretching process, the unit cell parameters, diffraction peak intensities and interplanar spacings of the samples all change regularly with the applied strain. The results of lattice response analysis show that the significant difference of the elastic limit in all directions of the alloy cell is the intrinsic cause of the first yield platform. The deformation process of the yield platform includes twin deformation and elastic deformation. The results of the study can well explain the shape memory effect of the alloy.