Microstructural Evolution of UNS S32205 Duplex Stainless Steel During Cold Rolling and Subsequent Annealing

Abstract

We followed the microstructural evolution of UNS S32205 duplex stainless steel during cold rolling up to 79% reduction in thickness and at early stages of isothermal annealing at 1080ºC. Qualitative analysis of peak broadening and kernel average misorientation (KAM) parameter obtained by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD), respectively, indicated a higher work hardening of austenite. Strain-induced martensite was not detected within this strain range by using X-ray diffraction and DC-magnetisation measurements. Two particular rolling thickness reductions were chosen for recrystallisation studies; i.e., 43% and 64%. After annealing for 1 min, primary recrystallisation occurred in ferrite (42% of recrystallised grains for 43% cold rolling), whereas austenite only recovered. For a reduction of 64%, the recrystallised fraction of ferrite did not change significantly, while austenite reached a recrystallised fraction of 43%. Full recrystallisation is noticed after annealing for 3 min for both conditions resulting in a bamboo-like grain structure.