Fine Grained Austenitic Stainless Steels: The Role Of Strain Induced α' Martensite And The Reversion Mechanism Limitations

摘要

The effect of the α'-strain induced martensite on the austenitic stainless steel grain size reduction is analyzed. Rolling with a 80% reduction factor at 200℃ and at 20℃ resulted respectively in a heavily deformed austenite and a mixed deformed austenite with α'-martensite bands. Further annealing treatments were carried out in the range of 20-880℃. Fine grains of about 1 μm can be obtained in the metastable austenitic stainless steel by a repetitive cold rolling and annealing thermomechanical process. In this case, reversion mechanism from deformation induced martensite α' to austenite γ is responsible for grain refining. Non-conventional warm rolling and annealing process can also lead to fine grains of 2μm without a reversion stage and as a result of recrystallization process of the strain-hardened austenite. The cold rolling route gives rise to a bimodal grain size distribution with a "lamellar" structure resembling to a "composite" material.