Misorientation Measurement in Tensile Test of Bimodal Harmonic Structured Stainless Steel by Diffraction Contrast Tomography Using Ultrabright Synchrotron Radiation X-ray

Abstract

Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was developed by powder metallurgy to improve both strength and ductility. In the present study, three-dimensional grain mapping for polycrystalline materials, called X-ray diffraction contrast tomography (DCT), was conducted at SPring-8, which is the brightest synchrotron radiation facility in Japan, to elucidate the deformation mechanism of harmonic structured JIS-SUS304L in tension. The average total misorientation tended to increase with stress in tensile tests; however, the total misorientation of the harmonic structured JIS-SUS304L was lower than that of JIS-SUS304L with a homogeneous distribution of coarse grains at comparable stress. Furthermore, the change in the crosssectional area of the harmonic structured JIS-SUS304L was also measured by refraction contrast tomography (RCT) imaging using SPring-8 in tensile tests.