A Study on Microstructural Evolution and Dynamic Recrystallization During Isothermal Deformation of a Ti-Modified Austenitic Stainless Steel

Abstract

Dynamic recrystallization (DRX) behavior in hot deformed (by uniaxial compression in a thermomechanical simulator in the temperatures range 1173 K to 1373 K [900°C to 1100°C]) Ti-modified austenitic stainless steel was studied using electron back scatter diffraction. Grain orientation spread with a ''cut off'' of 1 deg was a suitable criterion to partition dynamically recrystallized grains from the deformed matrix. The extent of DRX increased with strain and temperature, and a completely DRX microstructure with a fine grain size~4 lm (considering twins as grain boundaries) was obtained in the sample deformed to a strain of 0.8 at 1373 K (1100°C). The nucleation of new DRX grains occurred by the bulging of the parent grain boundary. The DRX grains were twinned, and a linear relationship was observed between the area fraction of DRX grains and the number fraction of R3 boundaries. The deviation from the ideal misorientation of R3 boundaries decreased with an increase in the fraction of R3 boundaries (as well as the area fraction of DRX) signifying that most R3 boundaries are newly nucleated during DRX. The generation of these R3 boundaries could account for the formation of annealing twins during DRX. The role of R3 twin boundaries on DRX is discussed.

Effect of temperatures and strain rates on the average size of grains refined by dynamic recrystallization for as-extruded 42CrMo steel

“…This implies that the substructure is 'dynamic' and readapts continuously to the increasing strain. At a critical strain, and correspondingly at a value/ variation in driving force, dynamically recrystallized grains appear at the original grain boundaries, which results in the so-called 'necklace structure' 12,13 . With further deformation, more and more potential nuclei are activated and new recrystallized grains appear 14,15 .…”

Influence of State of Stress on Dynamic Recrystallization in a Titanium-Modified Austenitic Stainless Steel

“…It is observed that DRX grains nucleate along prior grain boundaries by bulging mechanism, and this is similar to the nucleation mechanism observed in uniaxial compression of the same alloy. [2] The microstructural evolution at 1273 K (1000°C) reveals that DRX is marginal at 0.4 strain. However, a rapid progress of DRX at higher strains is observed at this deformation temperature because higher deformation SUMANTRA increases the defect density resulting in increased mechanical instability (i.e., higher driving force) in the microstructure.…”

“…In our recent study, microstructural evolution and DRX behavior in a Ti-modified austenitic stainless steel (referred to as alloy D9) during hot working was investigated over a range of temperature (1173 K to 1373 K [900°C to 1100°C]) and strain (0.2 to 0.8) at a strain rate 10 seconds À1 . [2] The nucleation of new DRX grains has been found to occur by bulging of the parent grain boundary. The processing parameters have been found to influence strongly the grain boundary character distribution and DRX in alloy D9.…”

An Investigation on the Softening Mechanism of 5754 Aluminum Alloy during Multistage Hot Deformation

“…The flow behaviors are very complex during hot deformation, and the parameters of hot deformation, such as temperature and strain rate, affect the flow stress significantly. Therefore, the control of deformation parameters is critical in optimizing the final mechanical properties [16][17][18][19][20]. Figure 4 indicates the true representative stress-stain curves of the studied alloy under various deformation conditions.…”