Development of creep damage evaluation method by three-dimensional grain mapping technique using synchrotron radiation

提出了一种多晶材料的三维晶粒成像技术，即X射线衍射衬度层析成像（DCT）技术。本研究在SPring-8上进行了DCT的测量，并对测量条件和数据处理进行了讨论。所开发的技术应用于铝合金和不锈钢。在SPring-8，BL 19 B2弯曲梁生产线上，利用该装置进行三维测绘，可以确定晶粒的形状和位置。接着，为了评价塑性变形，对各个晶粒的内部晶粒取向扩展进行计数。晶粒取向的扩展是由晶粒的镶嵌性引起的，这与微观结构的变化有关。随着塑性变形区拉应力的增加和循环载荷的增加，晶粒取向扩展程度增加。利用离散余弦变换技术，将晶粒取向扩展作为疲劳损伤参量之一，可以从微观结构上评价疲劳损伤，如裂纹萌生和蠕变损伤

The three dimensional grain mapping technique for polycrystalline material, that is termed X-ray diffraction contrast tomography (DCT) has proposed. In the present study, the measurements of DCT were conducted in SPring-8 and the condition of measurement and data procedure were discussed. Developed technique was applied to aluminum alloy and stainless steel. It was found that the shape and location of grain can be determined by three-dimensional mapping technique using the apparatus in SPring-8, BL19B2 bending beam line. Next, for evaluation of plastic deformation, the internal grain orientation spread of the individual grain was counted. The grain orientation spread is caused by the mosaicity, which related to the change of microstructure. The grain orientation spread increased with increasing in the tension stress in the plastic deformation region and cyclic loading. It is possible to evaluate fatigue damage in microstructure, such as crack initiation and creep damage, by the DCT technique and using the grain orientation spread as one of the fatigue damage parameters