Deformation characteristic and prediction of flow stress for as-cast 21Cr economical duplex stainless steel under hot compression

Hot compression tests in the temperature range from 1273 to 1423 K and strain rate range from 0.01 to 10 s–1 were carried out on a Gleeble 1500D thermo-mechanical simulator for as-cast 21Cr economical duplex stainless steel (EDSS). The deformation behavior and microstructural evolution were investigated. It is found that the flow behavior strongly depends on the strain rate and deformation temperature, and the flow stress increases with the increase of strain rate and the decrease of temperature. The softening degree of ferrite becomes larger with decreasing strain rate and increasing deformation temperature, and the austenite is gradually spheroidizing. The flow localization band easily happens at high strain rate and low temperature because of the uneven deformation in the microstructure. Moreover, the constitutive model with the compensation of strain was developed on the basis of hyperbolic sine equation to predict the flow stress of as-cast 21Cr EDSS. The material constant in the model such as α, n, Q and ln A was functioned with the strain by sixth order polynomial. The results show that the developed constitutive model has excellent predictability of flow stress under the experimental deformation conditions for as-cast 21Cr EDSS.