Effect of relaxation time on microstructural evolution of super austenitic stainless steel during multi-pass hot deformation

In present work, 00Cr25Ni19Mn6Mo7NCe super austenitic stainless steel (SASS) was subjected to three-pass hot compression. The deformation temperatures were 1200 °C, 1100 °C and 1000 °C, the strain rate was 1 s −1 , and the cooling rates between deformation passes were 5 °C/s and 1 °C/s to obtain different relaxation times of 20 s and 100 s. According to the results, the relaxation time significantly affected the flow behavior and microstructural evolution of the test steel during the third pass of deformation, which was related to static recovery, static recrystallization and meta-dynamic recrystallization during relaxation. On the premise that deformation behaviors of the first two passes were similar, the sample with the relaxation time of 100 s showed three softening behaviors upon the third pass, while that the sample with 20 s relaxation exhibited only two softening behaviors. This indicates that the number of deformation passes and relaxation time exert an important influence on the deformation mechanism of SASS. After three passes of deformation, the final microstructure of the sample exposed to 100 s of relaxation still existed original coarse grains. In contrast, the coarse grains disappeared and more dynamic recrystallized grains at third stage were formed in the sample with 20 s relaxation, and the recrystallization was more complete.