In Situ X-ray Diffraction Study of the Tensile Deformation of U-5.8Nb Alloy

摘要:

为了探明a2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。

Abstract:

The in situ X-ray diffraction (XRD) was used during uniaxial tensile loading to study the lattice response and deformation behavior of a2 U-5.8 wt% Nb (U5.8Nb) alloy. Diffraction patterns were recorded at incremental macroscopic strains until fracture of the sample, and the XRD data were analyzed by Rietveld method and single-peak fitting. The changes regulation of lattice parameter, diffraction peak intensity and interplanar spacing with applied stress during deformation were analyzed. It is found that the elastic deformation and the twinning deformation (reorientation) coexist in the initial stage of the first yield platform. The lattice response suggests that the remarkable anisotropy of elastic limit in various directions should be the genesis of double yield curve.