Strain-Induced Martensite Formation and Mechanical Properties of Fe–19Cr–4Ni–3Mn–0.15N–0.15C Austenitic Stainless Steel at Cryogenic Temperature

Abstract

Herein, considerable insight is provided into the evolution of strain-induced martensite and mechanical properties of Fe–19Cr–4Ni–3Mn–0.15N–0.15C wt% austenitic stainless steel (in short Cr19NC15.15) during deformation at room temperature and cryogenic temperatures. In situ magnetic measurements of the martensite evolution during tensile tests at various temperatures are conducted. The triggering stress (Formula presented.) required for strain-induced martensite formation is determined at the minimum in the strain hardening curve. It is found that with reducing deformation temperature in the range from 0 to –20 °C (Formula presented.) slightly decreases, whereas the triggering stress (Formula presented.) increases with further reduction of deformation temperature to −70 °C. The relation between the formed α′-martensite fraction and the strain applied during tensile test is established. The results demonstrate that a reduced deformation temperature from room temperature (RT) to −70 °C significantly enhances the transformation rate and the total volume fraction of strain-induced α′-martensite. The yield and tensile strength increase whereas elongation continuously decreases due to an increasing α′-martensite volume fraction with decreasing tensile test temperature. The α′-martensite formation kinetic follows Olson and Cohen's model and are in good agreement between the in situ experiment and theoretical calculations.