Effect of post deformation annealing on the microstructure and mechanical properties of cold rolled AISI 321 austenitic stainless steel

In the present research, the AISI 321 austenitic stainless steel was subjected to cold rolling with different amount of reductions. The 80% cold rolled samples were then annealed in the temperature range of 700-900 °C with different durations. The microstructural evolutions during cold rolling and subsequent annealing were investigated by XRD analysis, optical and scanning electron microscopy, and feritscope analysis. The mechanical properties were evaluated by room temperature tensile testing. Results showed that the amount of strain induced martensite is increased with increasing the rolling reduction. Annealing at 700 °C for 2 min resulted in the simultaneous increase of tensile strength and elongation due to the formation of ultrafine grain austenite. By annealing at 900 °C for 5, 10, and 15 min the bimodal grain structure was obtained as a result of the occurrence of static recrystallization and martensite to austenite reverse transformation simultaneously. Results of tensile testing showed that the good combination of strength and elongation is obtained by the formation of bimodal grain structure.