In situ neutron diffraction analysis of microstructural evolution-dependent stress response in austenitic stainless steel under cyclic plastic deformation

Understanding fatigue phenomena in metals is of great significance for mechanical performance in engineering systems. Microstructural evolution in austenitic stainless steels during cyclic plastic deformation has been studied via diffraction line profile analysis; however, their microstructure-dependent mechanical response upon stress partitioning in the matrix (austenite) and deformation-induced martensite has remained largely unexplored. In this study, the stress response analysis of austenitic stainless steel was performed using neutron diffraction. The phase stress in the austenite correlated well with the dislocation density in the phase. The actual stress in the martensite was nearly half of the assumed stress and the phase stress in the austenite. However, the apparent stress (the residual stress subtracted from the actual stress) was similar to the assumed stress as the martensite contains a fairly large compressive residual stress (approximately 1 GPa). Overall, the loading stresses at peak loads can be explained by sharing stress on the austenite and martensite.