Strain hardening behavior of metastable austenitic steel with TRIP effect; Insights from stress and strain partitioning

Mao, W.; Gao, S.*; Gong, W.   ; Bai, Y.*; Park, M.-H.*; Shibata, Akinobu*; Tsuji, Nobuhiro*

In this study, strain hardening behavior of Fe-24Ni-0.3C metastable austenitic steel having deformation induced martensitic transformation (DIMT) during deformation was investigated by tensile test with in-situ neutron diffraction, aiming to clarify the mechanism of the enhanced strain hardening caused by the DIMT. The results suggested that the evolution of phase stress of martensite during the deformation plays an important role in the strain hardening. It was found that during deformation the phase stress of martensite firstly increased rapidly from a low value, and then the rate of increase decreased as it approached 1.8 GPa. A dramatic increase in the stress partitioning between austenite and martensite was generated due to the rapid increase of martensite phase stress, which contributed significantly to the increase in the overall strain hardening rate of the material. The analysis of plastic deformation of austenite and martensite reveals that the rapid increase in stress partitioning occurred during the elasto-plastic deformation stage and arose from the occurrence of the plastic strain misfits.