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

Abstract

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 Xray 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.

Characterization of Evolution of Microscopic Stress and Strain in High-Manganese Twinning-Induced Plasticity Steel

“…[34][35][36][37][38][39] White X-ray diffraction method with microbeam synchrotron radiation has been also applied to observe the microstructure and to analyze the microscopic stress in steels. 40,41) This method has been employed to analyze the microscopic stresses evolved in the microstructure of iron-based shape memory alloys. The analysis showed that characteristic microscopic stresses are evolved by tensile deformation at room temperature and by subsequent annealing.…”

“…Laue diffraction patterns from a tensile sample with a low diffraction angle (2θ) of around 0.1° to 20° in the transmission Laue geometry were recorded during tensile testing using a flat panel detector. 41,42) For these measurements, small samples were prepared for the tensile test. The experimental set-up mainly consisted of an X-ray microbeam source, a tensile sample stage, a flat panel detector, and a Ge solid state detector (SSD), as reported previously.…”

“…The experimental set-up mainly consisted of an X-ray microbeam source, a tensile sample stage, a flat panel detector, and a Ge solid state detector (SSD), as reported previously. 41,42) In order to analyze the stress distribution in the sample under unloading after plastic deformation and under subsequent tensile loading, the Laue diffraction patterns were recorded for a sample unloaded after about 10% tensile deformation and for a sample loaded after subsequently being subjected to about 13% tensile deformation, as illustrated in Fig. 2.…”

“…The sample was deformed using a compact tensile machine for in-situ deformation. 40,41) The nominal tensile strain was measured from the displacement of marks indented on the tensile sample using an optical microscope. In white X-ray diffraction by in-situ tensile deformation, the applied load was measured using a load cell attached to the sample grip.…”

“…40) The value of d hkl was calculated from the obtained energy E hkl according to Bragg's law. 41) The value of ε hkl was calculated from the difference between the lattice spacing d hkl measured after deformation and the initial lattice spacing d 0 hkl . The resolution of the lattice strain was estimated to be ± 0.0004 ( ± 0.04%) from the strain measurement of a Si single crystal.…”