同步辐射衍射衬度断层成像方法学

The polycrystalline materials are the most widely used solid materials today. Their macroscopic properties are determined by the grain scale micro structures. X-ray diffraction contrast tomography(DCT) uses the grain diffraction as the contrast source of the grain 3D imaging. DCT provides access to the 3D shape, orientation, and elastic strain state of the individual grains and also can provide the grain boundary types and their 3D distribution. DCT research is at the initial stage in the world. .Our team designed and established a DCT imaging system at BSRF. We developed 2 series of prototype sample, Al and Mg. We already performed several times DCT imaging experiment. For the first time in the world, We study the characteristics of Friedel pairs in DCT under the condition that the rotation axis of sample is not exactly perpendicular to the incident X-ray direction. Based on this research, we developed the method of data processing considering rotation axis misalignment, which can significantly increases the correct matching and indexing proportions of the diffraction spots. A pure aluminum polycrystalline sample is investigated with 0.10°non-perpendicular angle of the rotation axis. The matching proportion of the spatial position of diffraction spots is increased to 90.62% from original 18.7%. .Our proposal will focus on the method to improve the orientation measurement accuracy of DCT and the tomography reconstruction accuracy of the grain. We also will develop the method and software of automatic treatment and analysis the diffraction information. We will boost the application research of DCT method in the Al polycrystals under the tension.

晶粒晶界的3D微结构决定了多晶材料的诸多使役性能。X射线衍射衬度断层成像（DCT）是目前唯一能无损获得多晶块体材料中晶粒的3D形状、晶面取向、晶界类型及其3D分布的新方法。世界DCT研究刚起步。我们建立了DCT成像方法学研究平台，完成了多轮DCT实验。在世界上首先发现：DCT成像中不同区域的Friedel对受样品偏轴影响的特征不同。据此建立了偏轴DCT成像参数修正及数据处理方法。对纯铝DCT的Friedel对预测的准确率从修正前的18.7%提高到90.6%。本课题将深入研究DCT成像晶面取向测量精度和晶粒断层重建精度等关键指标的影响因素和改进方法。系统研究DCT成像中衍射像斑的自动分割、自动指标化和配对等关键技术，发展自动处理软件。探索DCT引导下对感兴趣晶粒用线状光束的高角度衍射作直接断层形貌成像的方法学。改进仅适合方法学研究的DCT成像平台。开展示范性DCT应用研究，推广DCT的应用。

材料或部件的晶粒形状、尺寸、取向和晶界类型、分布等介观结构信息对其宏观性能的影响至关重要。3D无损的获取上述信息对很多研究和工艺优化研究具有重要意义。. 在本课题和BEPC国家实验室的资助下，本课题组在北京同步辐射装置BSRF的3W1线站建设了同步辐射硬X射线相衬成像和衍射成像实验研究装置，改进了入射同步辐射硬X射线的稳定性（采用了新型Laue双晶单色器）、提高了能量范围（采用了超导扭摆器光源）、改进了样品和探测器的支撑和调节装置，优化了实验方案，并研制了多尺度高分辨同步辐射白光成像探测器等。同时，本课题组还发展了用于衍射衬度CT（DCT）数据自动处理和重建的软件。上述工作大大推进了DCT的实用化。. 为了克服DCT成像观测面积过小的局限，本课题组发展了衍射消光成像和双能衍射成像方法，用于在较大面积上无损表征材料的晶粒取向、支晶特征和应变分布。在无损测量材料内部晶粒形貌的基础上，分析材料的应变分布，为材料或部件介观微结构的演化研究、工艺优化研究等提供了有效的新方法。. 本项目基本完成预期研究目标，已经发表文章2篇（SCI，标注），待发表文章3篇，已授权专利4项，其中发明专利2项，实用新型专利2项，还有3项专利在审核中。