Effect of reversion of strain induced martensite on microstructure and mechanical properties in an austenitic stainless steel

Abstract

Effect of reversion of strain induced α′ martensite on mechanical properties of an austenitic stainless steel has been examined. The α′ martensite formed by cold rolling (40%) at 0 °C has been reverted to austenite by carrying out annealing in the temperature range of 300–800 °C for 1 h. Microstructural investigation has demonstrated the enhanced reversion with increasing annealing temperature without any perceptible grain growth up to 800 °C. X-ray diffraction (XRD) analysis has revealed that 40% cold rolling has resulted in the formation of 32% martensite. The residual martensite content has been found to be about 8% after reversion at 800 °C. Different stages of reversion behavior has been examined by differential scanning calorimetric measurement. The variation of dσ/dε with ε is examined to identify different stages of work hardening of the investigated steel. Both tensile strength and percent elongation values increase with increasing annealing temperature up to 500 °C. Beyond that annealing treatment results in the drop of tensile strength value with the consequent increase in percent elongation. Attractive strength–ductility combination (22.80 GPa%) has been achieved after annealing of the 40% cold deformed specimen at 800 °C for 1 h. The fractographic observation corroborates the tensile results.