Effect of Nitrogen Addition on Strain Rate Dependence of Flow Stress in Austenitic Stainless Steels

Abstract

Effect of nitrogen addition on strain rate dependence of flow stress in austenitic stainless steel (SUS310S) was investigated. It is made clear that both thermal and athermal flow stress components are increased with increasing of nitrogen concentration. The flow stress was described by using the Kocks-Mecking (KM) model, where the KM parameters were determined from the data obtained by tension tests at low strain rates below RT. The flow stress at a high speed, 2×103 s-1 measured by the Hopkinson split-bar method agrees well with the prediction by the KM model. High nitrogen bearing steel is characterized by higher flow stress with a considerably large work-hardening at high speed deformation, which has never been achieved in ferritic steels. Because microstructure evolution is influenced by deformation temperature, flow stress shows the deformation history dependence in nitrogen bearing steels.