Study Of Multi-cycle Cold Rolling And Annealing Processing On Interface Character Distributions In Duplex Stainless Steel

The effects of multi-cycle cold-rolled-annealing treatments on the interface plane character distribution(IPCD) in duplex stainless steel UNS S32304 were studied by electron backscatter diffraction(EBSD), scanning electron microscopy(SEM) and optical microscopy(OM) techniques, and the intergranular corrosion resistance of the specimens as processed was evaluated by means of electrochemical workstation. The results show that, for the specimens having initial fully ferrite, the combined reaction of recovery of deformed α and precipitation of ? at nodes of recovered α occurs after multi-cycle cold rolling or single cold rolling plus high temperature annealing, especially in the specimens treated by two cycles of cold-rolling and annealing. The recovery process promotes the formation of low-angle grain boundaries(LAB) in the ferritic phase, and the nucleation and growth of ? introduces many PB with specific orientation relationship(OR) such as K-S and N-W. However, for the specimen with an initial(α+?) band microstructure, the recrystallization of both α and ? occurs simultaneously, accompanying a limited phase α?? transformation reaction after the same rolling and annealing. Most of high-angle grain boundaries(HAB) are generally in the ferrite, the specific orientation relationship between two phases seldom occurs and therefore the density of K-S or N-W phase boundaries was very low. The electrochemical corrosion tests show that the former specimens have higher intergranular corrosion resistance because LAB, twin boundaries(TB) and phase boundaries with specific ORs(K-S, N-W) exhibit excellent corrosion resistance.The microstructure evolution during annealing at 1050 ℃ in cold-rolled duplex stainless steel UNS 32304 was traced by means of off-line in-situ electron back scatter diffraction(EBSD) and scanning electron microscope(SEM) techniques. Austenite and ferrite exhibit different deformation resistance during cold rolling. Larger plastic deformation occurs in austenite than that in ferrite. Nearly half of austenite grains were strained via slipping on {111}<110> primary systems based on the slipping traces. The average misorientation between the grain pairs, which share the same location but are under different states of cold rolling and annealing for each phase, suggests that ferritic grains are more liable to recovery than austenitic ones during annealing at 1050℃ for 2 min. And also, further 5 min annealing brings about significant orientation changes for both phases, indicating that primary recrystallization occurred with a limited phase transformation.