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

Electron backscatter diffraction was used to observe the microstructure of an austenitic high-manganese twinning-induced plasticity steel and investigate the crystal orientation of grains in this steel. The results showed that mechanical twins are formed in a grain with a high Schmid factor during the tensile test. The orientation data obtained were used to estimate the anisotropic elasticity of the grains in the steel. The microscopic stress and strain evolved in the microstructure of the steel unloaded after plastic deformation were estimated using finite element method simulation in which the elastic anisotropy of the steel was taken into account. The simulation indicated that the evolution of microscopic stress and strain in the microstructure is considerably influenced by the crystal orientation of the grains. Furthermore, white X-ray diffraction with microbeam synchrotron radiation was used to characterize the evolution of microscopic stress and strain in the grains of the steel. The stress analysis during white X-ray diffraction indicated the formation of residual microscopic stress after tensile deformation, which was found to be distributed heterogeneously in the steel. It was also shown that the direction of the maximum principal stresses at different points in the microstructure under loading were mostly oriented along the tensile direction. These results are fairly consistent with the results obtained by the simulation, although absolute values of the real principal stresses may be influenced by the heterogeneously evolved strain and the several assumptions used in the simulation.