Formation of ultrafine grained microstructure in the austenitic stainless steel and its impact on tensile properties

Commercial grade AISI 316L austenitic stainless steel was heavily cold rolled to 90% of thickness reduction. The cold rolled material was subjected to repetitive annealing treatment for short duration of 45-60 s at various temperatures. The microstructure of the cold rolled and after annealing was studied by optical as well as transmission electron microscope. The microstructural examination of the specimens after repetitive annealing process revealed the formation of ultrafine grain size microstructure. It was also noted that depending on the processing condition the grain size distribution varied widely. The tensile testing of the annealed specimen showed that the yield strength increased by 4-5 times that of the coarse grained material. However, a loss in the strain hardening ability was observed in these specimens. A good combination of yield strength and ductility for ultrafine grained stainless steel as compared to the coarse grained material could be obtained by the optimization of the microstructure.