Microstrain and boundary misorientation evolution for recrystallized super DSS after deformation

Abstract

After deformation, super duplex stainless steel (DSS) was annealed at 1100 °C for a two-phase solid–solution region to avoid σ formation. Preferred orientations in δ and γ phases changed to (111)δ, (100)δ, and (101)γ from the rough random orientation of as-received super DSS. The kernel average misorientation (KAM) angle was less than 5° implying the grain boundary misorientation strain shifted to a higher value after cold rolling, which was consistent with the X-ray diffraction (XRD) microstrain results. After annealing, the misoriented angle was restored to a low angle of approximately 0.5°, which implied elimination of grain boundary misorientation strain when the annealing time increased from 15 to 30 min. The calculated microstrain based on XRD peaks demonstrated that the γ phase deformed before the δ phase at 50% CR. The recrystallized δ grains with slow growth and high staking fault energy (SFE) mainly showed dynamic recovery and a wide misorientation distribution of high angle grain boundary (HAGB) in the range between 15° and 58°, whereas the recrystallized γ grains with low SFE exhibited rapid dynamic recrystallization; the angles of the most HAGB grains were greater than 50°, because of the dissipation of the stored strain energy. This recrystallized austenite adhered to the Kurdjumov–Sachs relationship with ferrite.