EBSD Study of the Microstructural Evolution during Hot Compression Testing of a Superduplex Steel

Abstract

Superduplex steels exhibit a microstructure of approximately equivalent fractions of austenite and δ-ferrite. This structure combines a higher strength than austenitic steels with a higher toughness than ferritic steels and an excellent corrosion resistance. Superduplex steels can be processed by different routes such as casting, extrusion, rolling or forging and are applied in the chemical industry, oil production or paper manufacturing. It is well known that the two phases exhibit a different dynamic restoration behavior due to their differences in the stacking fault energy. The austenite grains are more likely to undergo discontinuous dynamic recrystallization while the δ-ferrite grains tend to strong dynamic recovery. Modern large area electron back scatter diffraction (EBSD) scans are a powerful technique to study the microstructural evolution of the individual phases during hot-forming of duplex steels. However, detailed EBSD studies explaining the flow behavior, influence of grain orientation and grain size modification during hot forming have not been carried out yet. In the present investigation specimens of a S32750 superduplex steel were deformed in uniaxial compression with strain rates between 0.01 and 1 [s-1] to a true strain of 1 at temperatures between 1000 and 1300°C. The microstructures of the as-deformed specimens were examined by large area EBSD scans with particular attention to the characteristics of the individual phases as for example grain size and stored energy of the austenite grains or subgrain size and grain boundary character of the ferrite grains. The differences due to deformation temperature and strain rate are discussed.

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

“…However, in order to widen the applications of DSS, it is important to understand the evolution of microstructure, texture, and properties during thermo‐mechanical processing of DSS. Several investigations have been carried out to understand hot‐deformation and cold‐rolling and annealing behavior of DSS . It has been argued that the two phases deform independently, and the evolution of microstructure and texture can be inferred from the behavior of single‐phase materials .…”

Microstructure Evolution during Hot Deformation of UNS S32750 Super-Duplex Stainless Steel Alloy

“…In the case of SDSS, both stresses and strains from the applied hot working regime are unevenly distributed in ferrite δ and austenite γ due to the lower capability of plastic deformation accommodation of ferrite than that of austenite. This triggers different deformation behavior for degrees of deformation [11][12][13][14][15]. It has been reported that, in the case of applied recrystallization treatments prior to hot deformation processing, the initial grains of γ austenite are smaller than the grains of δ ferrite, with a direct repercussion on the microstructure of the alloy that was obtained after hot deformation, resulting in a more homogenous deformed γ austenite phase compared to the δ ferrite phase [16,17].…”