Mechanisms of the Reverse Martensite-to-Austenite Transformation in a Metastable Austenitic Stainless Steel

The martensite-to-austenite reversion mechanisms under continuous heating and annealing of metastable austenitic stainless steel subjected to cold swaging were studied. reversion-temperature-time diagram was constructed using high-resolution dilatometry. revealed a sequence martensitic diffusional recrystallization. Martensitic might be separated by the rate >10 °C/s. started via mechanism, mechanism developed during subsequent heating. However, both enhance simultaneously at slow rates (<10 °C/s). At higher temperatures, recrystallization occurred. Post-mortem microstructure analysis has allowed classifying reverse modes into low- (500–650 °C), medium- (~700 high-temperature (~800 °C) regimes. During low-temperature annealing, development phase reversion, recovery, recrystallization, carbide precipitation characterized high amount new austenite grains restriction their growth that resulted in formation an ultrafine grain structure with average size 100–200 nm. Medium-temperature associated almost fully recrystallized structure, but lamellar regions still detected. Austenitic dissolution particles enhanced annealing.