Microstructure and texture evolutions of 310S austenitic stainless steel after cryogenic rolling and subsequent annealing: X-ray and electron backscatter diffraction studies

The present work aims to study the microstructure and texture evolutions of thermomechanically processed 310S austenitic stainless steel. The material was cryo-rolled at 20%, 50% and 90% thickness reduction, followed by annealing at 1023, 1223 and 1323 K for 5, 15 and 30 min, respectively. After a 20% thickness reduction, strain-induced alpha '-martensite was seen along with deformation twinning within the austenite grains. The volume fraction of the deformation twinning was higher than that of alpha '-martensite. By increasing deformation from 50% to 90%, the volume fraction of alpha '-martensite went from 11% to 69%, and twinning was replaced by martensite. Brass, Goss, and S components were the dominant textures in the austenite phase after deformation, while the main texture components in alpha '-martensite were R-Cu, R-cube, F, and E. Brass component was further increased by increasing the thickness reduction in contrast to the Goss component. During annealing, martensite to austenite reversion and recrystallization occurred in the deformed austenite, which resulted in an increase in the volume fractions of the Goss and Brass recrystallization components. However, the annealing texture of the alloy was found to be approximately the same as the cryo-rolling texture. The kinetics of martensite reversion at 1223 K for 5 min was much faster than that at 1023 K. An equiaxed microstructure was not detected at 1023 K for 5 min due to incomplete martensite reversion and primary recrystallization. The optimum annealing temperature for obtaining an ultrafine grain structure was 1023 K for 15 min. Recrystallization and tangible grain growth swiftly occurred at 1173 K and 1273 K.

Automated summary

The study investigates the microstructure and texture changes of thermomechanically processed 310S austenitic stainless steel. Cryo-rolling with different thickness reductions and subsequent annealing were conducted. Deformation twinning and strain-induced alpha'-martensite were observed after 20% thickness reduction, with higher volume fraction of twinning. With increased deformation, martensite replaced twinning and the volume fraction of martensite increased. Brass, Goss, and S components were dominant textures in the austenite phase, while R-Cu, R-cube, F, and E were the main components in alpha'-martensite. Annealing led to martensite to austenite reversion and recrystallization in the deformed austenite, resulting in increased fractions of Goss and Brass recrystallization components. The annealing texture was similar to the cryo-rolling texture. Martensite reversion was faster at 1223 K for 5 min compared to 1023 K. The optimum annealing temperature for an ultrafine grain structure was found to be 1023 K for 15 min.