Evolution of Microstructure and Texture during Isothermal Annealing of a Heavily Warm-rolled Duplex Steel

Abstract

The evolution of microstructure and texture during isothermal annealing of a heavily warm-rolled duplex steel (DSS) was studied. For this purpose a DSS steel was hot rolled, homogenized at 1 448 K and subsequently warm-rolled to 90% reduction in thickness at 698 K and 898 K. This was followed by isothermal annealing at 1 448 K for different time intervals up to 7 200 seconds. Lamellar microstructure with alternate arrangement of deformed ferrite and austenite bands was observed in the as warm-rolled condition.The ferrite in DSS warm-rolled at 698 K showed much stronger α-fiber (Rolling direction (RD)//<110>) than γ -fiber (Normal direction (ND)//<111>) as compared to the ferrite in DSS warm-rolled at 898 K. The austenite in warm-rolled DSS showed a predominantly pure metal (or copper type) texture. Upon annealing the lamellar morphology of the as warm-rolled structure transformed into a bamboo type morphology for short annealing time but finally broke down with increasing isothermal annealing time due to mutual interpenetration of the two phases. Retention of deformation texture components and presence of annealing twins in austenite indicated discontinuous recrystallization. Despite differences of texture in the as warm-rolled condition the ferrite in annealed DSS showed much stronger α-fiber as compared to γ -fiber due to strong recovery behavior of ferrite during annealing. The texture evolution in the two phases was not affected by the presence of the other phase while grain growth was significantly restricted due to the presence of the other phase.

Microstructure, Texture, and Tensile Properties of a Severely Warm‐Rolled and Annealed Duplex Stainless Steel

“…Recently, the evolution of microstructure and texture in DSS during warm‐rolling has been reported by the present authors . It has been demonstrated that DSS can be successfully processed by warm‐working to 90% reduction in thickness, avoiding the deformation‐induced transformation of austenite.…”

“…The two phases of warm‐rolled DSS during isothermal annealing show different softening behavior. Ferrite shows predominantly recovery‐type behavior in contrast to discontinuous recrystallization in austenite . In the warm‐rolled material, ferrite has a low misorientation build‐up inside the ferrite bands such that the subgrains are separated by LABs.…”

“…The retention of deformation texture in austenite in different warm‐rolled and annealed DSS indicates discontinuous recrystallization, but absence of preferential orientation selection. Nucleation from pre‐existing orientations in the deformed matrix but no preferential orientation selection would result in a situation where the annealing texture should be a random sampling of the deformation texture . Thus, the observed differences in the texture of austenite originate from the existing differences in the texture of austenite in DSS warm‐rolled to different reduction in thickness.…”

Simultaneous Strength-Ductility Enhancement of a Nano-Lamellar AlCoCrFeNi2.1 Eutectic High Entropy Alloy by Cryo-Rolling and Annealing

“…However, the microstructures of the cryo- and cold-rolled materials are strikingly dissimilar after annealing. The cold-rolled material shows a rather homogenous ultrafine microduplex structure after annealing due to the breakdown of lamellar deformation structure, typically observed in cold-rolled and annealed duplex alloys 44 . In sharp contrast, the cryo-rolled material after annealing shows a distinctly heterogeneous hierarchical microstructure and unprecedented tensile properties.…”

Ultrafine-Grained AlCoCrFeNi2.1Eutectic High-Entropy Alloy

“…Furthermore, the growth of one phase is inhibited by the presence of the other phase, typically observed in duplex alloys. [24] The change in the phase fraction observed after annealing is also found in other duplex alloys as the equilibrium phase fraction is determined by the annealing temperature. [25] The evolution of recrystallized UFG duplex microstructure in the EHEA thus appears to be quite consistent with these findings.…”