Hot deformation behavior of ferrite and austenite phases of ferritic stainless steel in the duplex temperature range

A novel approach was proposed to elucidate hot flow stress of ferritic and austenitic duplex alloys by employing ferritic stainless steel in the duplex temperature range. Hot compression tests of 16%–18% Cr stainless steel were conducted in the temperature range from 823 °C to 1250 °C. SUS430 in this temperature range can be used to investigate the flow curve of the austenite–ferrite coexisting state and ferrite single-phase regions above and below the duplex temperature. The hot deformation behavior in the α-single phase (body-centered cubic, ferrite) region of SUS430 was compared with SUS430LX and found to be equivalent. The form of the flow curve identified by the inverse analysis to correct for temperature and deformation inhomogeneities during the compression tests changed owing to the presence of the γ-phase (face-centered cubic, austenite), which was not visible in the axial stress–strain curve obtained by the hot compression tests. The obtained flow stress parameters were subjected to regression analysis, which made it possible to describe quantitatively the effects of γ-phase precipitation on the flow curve. Observations of the internal microstructure revealed the differences in deformation mechanisms of the α-single phase and the α+γ duplex region. • Hot flow stress of duplex region in ferritic stainless steel was studied. • The inverse analysis of the compression test clarified changes in flow curve. • The flow curve changed owing to the γ-phase in α+γ duplex region. • The effects of γ-phase precipitation on the flow curve were described quantitively. • The deformation mechanisms in α-single and α+γ duplex regions were elucidated.