Evaluation of Internal Stress in Individual Grains of Cold-Rolled Stainless Steel by Energy Dispersive X-ray Diffraction

概要

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The X-ray diffraction technique for measuring the microscopic-scale distribution of internal stress in grains of polycrystalline metal was developed in order to investigate the mechanism of the intergranular stress corrosion cracking in non-sensitized stainless steel. This technique utilized the energy dispersive X-ray diffraction with white X-ray micro beam. It enabled to evaluate elastic strain occurring in each grain distorted by cold rolling. The materials were cold-rolled in one dimension to produce 20% reduction in thickness at room temperature. The internal stress of individual grains in 20% cold-rolled SUS316 stainless steel was evaluated applying external tensile stress up to 380 MPa over elastic limit. The result indicated the inhomogeneous microscopic-scale distribution of internal stress in grains. The residual stress was distributed dispersedly to each grain in the range from compressive stress of about –500 MPa to tensile stress of about 400 MPa. The distribution of applied tensile stress to each grain was inhomogeneous.