Accurate determination of grain properties using three-dimensional synchrotron X-ray diffraction: A comparison with EBSD

The characterization of elastic strain and stress at the grain level is becoming an important route for validating meso- and nano-scale numerical models. The response of a grain to a mechanical load depends not only on the elastic and plastic properties of the single crystal, but also on the interaction of the grain with its local neigh-borhood. In this paper, an in-situ three-dimensional synchrotron X-ray diffraction experiment is conducted on a polycrystalline zirconium specimen. The data obtained from the experiment are used to develop methods to reconstruct three-dimensional grain maps by adding the grain layers measured by a planar X-ray beam, and to track individual grains across loading steps. The measured center-of-the-mass and volume of each grain are subsequently used to reconstruct 3D grain boundaries using the weighted Voronoi technique, and to determine grain neighborhoods. The results from the developed post-processing methods are compared against those measured using electron backscatter diffraction (EBSD) technique. It is shown that with the use of the developed methods, both small and big grains are accurately determined with 3D-XRD. It is further shown that the accuracy of the implemented Vomnoi technique in determining the right grain neighborhood is more than 80%.

在晶粒层面表征弹性应变和应力正成为验证介观和纳米尺度数值模型的重要途径。晶粒对机械载荷的响应不仅取决于单晶的弹性和塑性性质，还取决于晶粒与其局部邻域的相互作用。在本文中，对一个多晶锆试样进行了原位三维同步辐射X射线衍射实验。从实验中获得的数据被用于开发通过添加平面X射线束测量的晶粒层来重建三维晶粒图的方法，以及在加载步骤中追踪单个晶粒的方法。随后，利用加权沃罗诺伊（Voronoi）技术，将测量到的每个晶粒的质心和体积用于重建三维晶界以及确定晶粒邻域。将所开发的后处理方法得到的结果与使用电子背散射衍射（EBSD）技术测量的结果进行了比较。结果表明，使用所开发的方法，利用三维X射线衍射（3D - XRD）能够准确地确定大小晶粒。进一步表明，所实施的沃罗诺伊技术在确定正确的晶粒邻域方面的准确率超过80%。