The formation of bimodal microstructure in a 316L austenitic steel subjected to large strain cold rolling and subsequent annealing and its effect on the mechanical properties were studied. The cold rolling was accompanied by the strain-induced martensitic transformation and grain refinement. The strain-induced martensite comprised 25 % after rolling to a total strain of 3. The deformation microstructures consisted of flattened austenite / martensite grains with the transverse grain sizes of about 130 nm. The steel with nanocrystalline structure exhibited high yield strength (σ0.2 = 1680 MPa), but low total elongation (δ = 5 %). The subsequent annealing was accompanied by austenite reversal, static recrystallization and grain growth. The annealing at a temperature of 700 °C (2 hours) led to a fully austenitic structure with bimodal grain size distribution. This bimodal microstructure consisted of individual micrometer-sized grains surrounded by the nanocrystalline matrix. The development of bimodal microstructure resulted in an increase of the total elongation above 15 % while maintaining high strength (σ0.2 = 960 MPa).Keywords: Austenitic stainless steel, cold rolling, grain refinement, annealing, recrystallization
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