Study On Microstructure And Property Evolution Of LDX2101during Thermal Deformation

Duplex stainless steels (DSSs) were processed to have a balanced microstructure containing approximately equal amounts of ferrite and austenite, which exhibit exceptional mechanical properties and corrosion resistance. Lean duplex stainless steel (LDX)2101with lower contents of Ni and Mo had been developed in order to further reduce the cost. However, the coexistence of ferrite and austenite during hot deformation led to a complicated deformation behavior, and little research had been dedicated to studying the microstructure evolution in LDX2101compared with traditional DSSs. The microstructure, menchanical and corrosion properties evolution of the LDX2101during hot rolling were studied by thermo-mechanical simulate tests, using optical microscope, scanning electron microscopy, and electron backscatter diffraction technique. This research has drawn the following conclusions:1. The flow curve characteristics of LDX2101during hot deformation were interpreted by coupling behaviors of the microstructure evolution in its both phases. Continuous dynamic recrystallization occurred both in ferrite and austenite phases by gradual transformation of low angle grain boundaries into high angle grain boundary. Hot compression textures of the constituent phases showing that the brass-type texture, typical of f.c.c materials with low SFE, is developed in the austenite phase, and the rotated-cube texture is developed in the ferrite phase. The differences in the microstructure and texture evolution features under different hot deformation modes can be explained by the differences in softening mechanisms.2. The austenite phase was evenly distributed as islands in the ferrite matrix and elongated along the rolling direction, with the hot rolling reduction rate increased, the deformation textures decreased and recrystallization textures increased in both phases, leading to the decrease in texture intensities. Steels with higher reduction ratios showed lower pitting potentials and higher average corrosion rates. Relatively high frequency of low S coincidence site lattice grain boundaries appeared in steels with reduction ratios less than or equal to80%, especially in austenite phase, fraction of S3-S29grain boundaries reached approximately35%, leading to the better overall properties.3. After solution treatment, the texture components of ferrite phase were composed by deformation texture and phase transformation texture, and texture components of austenite phase were composed by deformation texture and recrystallization texture, the texture intensity of ferrite phase was greater than that of austenite phase. Under solution treatment at1050～1100℃, the phase volume fraction ratio of ferrite and austenite phases was approximately1:1, the nano-indentation hardness values were closer, the texture intensity defference was smaller, conducive to the following deformation of2101duplex stainless steel hotrolled plate.