Hot deformation behavior of 309L stainless steel

Abstract

Hot compression tests were carried out on 309 L austenitic stainless steel at different deformation temperatures (900–1100 ℃) and different strain rates (0.01–10 s−1). Based on the stress-strain curve, three constitutive models, Modified Johnson-Cook, Modified Zerilli–Armstrong and Strain Compensation Arrhenius, are constructed, and it is found that the Strain Compensation Arrhenius model has the highest accuracy. Besides, the Arrhenius model and the dynamic material model were adopted to construct the activation energy map and power dissipation map of 309 L stainless steel with different strains. In the region with high temperatures and high strain rates, low activation energy Q value and high power dissipation η value were shown. According to the microstructure, the deformation of ferrite and austenite phases was uniform at 1050 and 1100 ℃/10 s−1, the level of recrystallization fraction was high, and the grains were fine and uniform. However, at 900 ℃/10 s−1, the microstructure suffered serious distortion, the ferrite was significantly elongated, and cracking occurred at the phase boundaries. A conceptual processing map was built through the prediction of activation energy map, power dissipation map and analysis of microstructure in combination. The optimal hot working range was 1025–1100 ℃/2.7–10 s−1, and the instability region was 900–958 ℃/0.28–10 s−1.