Formation of nano/ultrafine grain structure in a 201 stainless steel through the repetitive martensite thermomechanical treatment

摘要

The nano/ultrafine grained 201 austenitic stainless steel was produced via the martensite thermo mechanical treatment. This treatment is consisted of two stages of cold rolling followed by reversion annealing. In this work, effect of repetition of the process on grain refinement and the resulted mechanical properties were investigated. The first stage was consisted of cold rolling to 70% thickness reduction followed by annealing at 850 ℃ for 60 s, while the second stage was comprised of cold rolling to 60% thickness reduction followed by annealing at 850 ℃ up to 60s. The smallest grain size of 80 ± 10 nm with a microstructure consisted of austenite and small amount of retained martensite was achieved by secondary annealing for 30 s. Increasing the annealing time to 60 s, led to the formation of fully austenitic microstructure but the grain size of about 260 + 40 nm. This microstructure possessed the yield strength of 1 GPa and the total elongation of 30%.