3D/4D imaging of crystal structures

Fig. 1 Process of grain boundary tracking

@Methods of 3D mapping of crystal orientation include 3D X-ray diffraction microscopy, which is being energetically developed by the study group of Risoe in Denmark. However, it is theoretically difficult to analyze materials under deformation using 3D X-ray diffraction microscopy, due to blurring of the diffraction mottles. On the other hand, we are developing a 4D method for measuring the crystal deformation behaviors of materials, in which pencil beam XRD is combined with 4D CT imaging. By combining the grain boundary visualization technology described in gHigh resolution imaginghand the microstructure characteristic tracking technology described in g4D mapping of internal mechanical quantitiesh,we have developed a 4D tracking technology for determining crystal grain deformation behaviors within materials (Paper 1), and call it grain boundary tracking.

Fig. 2 Visualization of interactions (mismatch of distortion) between adjacent crystal grains through grain boundary tracking

@In grain boundary tracking, 4D images of such things as deformation fractures are obtained, as shown in Fig. 1, and are visualized by decorating the grain boundaries with gallium, etc. Then all the pixels are classified into those on the grain boundaries and those within grains, based on the grain boundary images. A closed crystal grain shape is reconstructed by connecting the grain boundary pixels, and the 4D deformation behaviors of the grain are visualized by tracking the grain boundary pixels. The distribution of distortion inside each grain can also be measured at the same time by tracking the intragranular pixels.

Fig. 3 Pencil beam scanning XRD to be combined with grain boundary tracking

@As shown in Fig. 3, we are proposing to combine 3D XRD that uses pencil beam scanning, with grain boundary tracking, to allot crystal orientations to all crystal grains obtained(Paper 2).This will sharply improve the precision of grain boundary detection and reconstruction of grain shapes, and will offer an innovative crystallographic method that can be used for investigating deformed materials. We will develop the technology into one without equal in the world, appropriate for assessing the mechanical behaviors of structural materials.

Review paper

  1. H. Toda, M. Kobayashi, Y. Suzuki, A. Takeuchi, K. Uesugi, 3D¥4D Materials Science: Its Current State and Prospects, Hihakaikensa, Vol.58CNo.10C2009C433-438
  2. H. Toda, M. Sato, H. Okuda, M. Kobayashi, Observation and analysis of materials with synchrotron radiation, Keikinzoku Vol.61, No.1, 2011

Research paper

  1. H. Toda, Y. Okawa, M. Kobayashi, K. Uesugi and Y. Suzuki, Acta Materialia, to be submitted.
  2. H. Toda, D. LeClere, Y. Okawa, M. Kobayashi, K. Uesugi and Y. Suzuki, Acta Materialia, to be submitted.