Microstructure Refinement of 301 Stainless Steel via Thermomechanical Processing

The current study applied thermomechanical processing (TMP) on 301 austenitic stainless steel to produce an ultrafine-grained structure, examining the dual effects of deformation at subzero temperature and TMP cycles strain-induced α′-martensitic transformation austenite reversion occurring upon subsequent annealing. Three schemes were adopted: (1) one cycle using a strain 0.30, (2) two 0.20, (3) three 0.15. Each consisted tensile −50 °C followed by annealing 850 for 5 min. Compared other schemes, use 0.15 scheme resulted in significant formation martensitic phase about 99 vol.%. Consequently, occurred strongly, providing mixture structure reverted ultra-fine grains retained coarse with average grain size 1.9 µm. development mixed was found lower stability thus enhance cycles. Moderate growth high-angle boundaries all reaching maximum 64% 3 scheme. behavior during generally characterized initial hardening slip (stage I), remarkable increase rate due II). Further straining promoted breakage α′-martensite banded lath forming dislocation cell-type martensite, which marked decline III). Accordingly, latter stage had lesser hardness enhancement deformed samples increasing number Nevertheless, yield strength processed improved from 450 MPa 1 515 3.