Hot deformation behavior of 2707 hyper duplex stainless steel

The hot deformation behavior of 2707 hyper duplex stainless steel (HDSS) was investigated through a hot compression test at 950 °C to 1,250 °C at strain rates of 0.01 s−1 to 10 s−1. Observations from the flow stress curves reveal a balance between work hardening and dynamic recovery at the beginning of the deformation and subsequently demonstrate various softening mechanisms with the increase of strain. At high strain rates, dynamic recovery is the prevailing mechanism, whereas, at medium and low strain rates, dynamic recrystallization becomes dominant. The constitutive equation was constructed, and the deformation activation energy was calculated to be 645.46 kJ·mol−1. The hot processing map was drawn based on the dynamic material model at a strain of 0.8. The results indicate that the hot workability of 2707 HDSS decreases due to its high alloying content. The microstructure evolution of 2707 HDSS at 1,050 °C was identified by means of electron backscatter diffraction and transmission electron microscopy. The results demonstrate that the ferrite completes dynamic recrystallization at the strain rate of 1 s−1. The softening process of austenite is influenced by ferrite and mainly experiences dynamic recovery. The austenite located at the α/γ phase boundaries tends to undergo dynamic recrystallization.