Ultrafine grained microstructure tailoring in austenitic stainless steel for enhanced plasticity

• Processing of ultrafine grain size by repeated annealing cycles.
• Microstructure tailoring at ultrafine grain size regime.
• Processing bimodal type grain size distribution in ultrafine grained microstructure.
• Effect of grain size distribution on plasticity.

Using repeated or cyclic annealing process a recrystallised ultrafine grained microstructure possessing high strength and a reasonable ductility was obtained from a heavily cold rolled Austenitic Stainless Steel. Johnson Mehl Avrami and Kolmogorov model for predicting recrystallisation process was used to optimize the process parameters for the formation of ultra-fine grained recrystallised microstructure. The microstructure evolving during thermal cycling was analyzed by electron microscopy. The tensile properties of various ultrafine grained microstructures were determined. Electron microscopy studies on tensile deformed specimens showed that there is a narrow dispersion in grain size distribution of ultrafine grained microstructure which promotes shear banding or strain localization causing impairment of the ductility or poor plastic strain hardenability.