Solid solution-hardening by hydrogen in Fe–Cr–Ni-based austenitic steel studied by strain rate sensitivity measurement: Contributions of effective stress and solute drag

Abstract

Dissolution of atomic hydrogen (H) into Fe–Cr–Ni austenitic steels causes a significant increase in flow stress (i.e., solid solution-hardening, SSH) during their plastic deformation. In this study, the characteristics and kinetics of H-induced SSH in AISI Type310S steel with 7600 at ppm H were studied through the measurements of strain rate sensitivity, S, by stress relaxation and strain rate jump experiments at 296 K. Two factors were found to contribute to the SSH: (i) the role of H as thermally activatable obstacles that increases the effective stress; (ii) the resistance acting on moving dislocations due to their dragging of H atmosphere (solute drag). These factors operated cooperatively or competitively in determining the S value and its dependencies on stress, strain, and strain rate. The peak SSH can be achieved where the sum of dislocation glide resistances from (i) and (ii) is maximized. The anticipated strain rate range for establishing such a situation coincided accurately with the author's previous experiments.