Flow Softening and Microstructure Evolution of Austenitic Stainless Steel during Hot Compression

Hot compression experiments were conducted on AISI-304L austenitic stainless steel at strain rates of 0.01 and 10 s–1 within the temperature range of 900 to 1200°C, up to a strain of 0.69. Discontinuous dynamic recrystallization (DDRX) plays a significant role in the hot deformation process of AISI 304L ASS, while continuous dynamic recrystallization (CDRX) only plays a synergistic role. As the deformation temperature rises, the fraction of recrystallization (RX) nucleation consistently increases. At the same deformation temperature, the fraction of RX first decreases and then increases with increasing strain rate. The higher fraction of RX occurs at lower strain rates because more deformation time is available for grain boundary migration. At a higher strain rate, the higher stored energy, adiabatic temperature rise (ATR), and post-dynamic recrystallization (PDRX) promote the RX process. Flow stress curves were revised considering the effects of adiabatic heating during hot deformation. The results showed that ATR is improved with increased strain level attained, strain rate, and temperature decrease.