Investigation on the strain hardening behavior, strain rate sensitivity and hot deformation maps of AISI 321 austenitic stainless steel

In the present research, the hot compression tests were performed on AISI 321 austenitic stainless steel in the deformation temperature range of 800-1200˚C and constant strain rates of 0.001, 0.01, 0.1, and 1 s^-1. The hot flow curves were utilized for determination of the strain hardening exponent, strain rate sensitivity exponent and construction of the processing maps. Variation of the strain hardening exponent with strain was used for prediction of the microstructural evolutions during hot deformation. Four types of variations were distinguished which reflect the occurrence of dynamic recovery, single and multiple peak dynamic recrystallization and the interaction between dynamic recrystallization and precipitation. Also, the strain rate sensitivity variations at the applied strain of 0.8 and strain rate of 0.1 s^-1 was compared with microstructural evolutions and the results demonstrated the existence of reliable connection between this parameter and evolved microstructures. Furthermore, the power dissipation map at the applied strain of 0.8 was compared with the resultant microstructures at some predetermined deformation conditions. It was concluded that the microstructural evolutions is shifted from complete to partial dynamic recrystallization and dynamic recovery with increasing the power dissipation ratio.