Hot deformation and restoration mechanisms in duplex stainless steels: effect of strain rate

In the current study, the microstructural evolution has been investigated for a 2205 duplex stainless steel during uniaxial hot compression at a temperature of 1000 C at different strain rates in the range of 0.1-50 s−1. It was found that the strain rate changed the dynamic restoration mechanism in ferrite. At strain rates below 1 s-1, ferrite underwent continuous dynamic recrystallization characterized by a gradual increase in misorientation angles between adjacent subgrains. When the strain rate exceeded the above value, ferrite tended to soften through the discontinuous dynamic recrystallization (DDRX) mechanism associated with nucleation and growth of new grains. Austenite showed rather similar microstructure characteristics for different strain rates. The majority of austenitic grains experienced dynamic recovery accompanied at high strain values by a small fraction of new DDRX grains. The main feature of the austenite phase was the profuse formation of deformation bands separated by transition regions and locally containing microband (MB) arrays. It was found that, independent of the orientation of austenite grains, MB boundaries were typically aligned with high Schmid factor {111} slip planes.