Anomalous plastic deformation and martensitic transformation in metastable austenitic steels at low strain rate characterized by in-situ hydrogen and argon releases and scanning probe microscopy

Abstract

Plastic deformation behavior and strain-induced martensite (α’) transformation in metastable austenitic stainless steel sheets are investigated during tensile loading at a slow strain rate of 1.7 × 10−4 s−1 at 298 K by in situ hydrogen and argon releases and scanning probe microscopy. Anomalous stress peaks, which occur on the stress-strain curve in the later half stage of plastic deformation, are simultaneous with distinct hydrogen release peaks and argon release valleys, and the α’ content measured at a fixed region increases stepwisely with increasing strain in the corresponding stage of deformation. Such anomalous deformation and α’ transformation phenomena result from repeatedly occurring and propagating of X-shaped strain localization accompanied by the rapid α’ transformation in the later half stage of deformation.