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

摘要

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.