Modeling the Flow Behavior, Recrystallization, and Crystallographic Texture in Hot-Deformed Fe-30 Wt Pct Ni Austenite

Abstract

The present work describes a hybrid modeling approach developed for predicting the flow behavior, recrystallization characteristics, and crystallographic texture evolution in a Fe-30 wt pct Ni austenitic model alloy subjected to hot plane strain compression. A series of compression tests were performed at temperatures between 850°C and 1050°C and strain rates between 0.1 and 10 s -1 . The evolution of grain structure, crystallographic texture, and dislocation substructure was characterized in detail for a deformation temperature of 950°C and strain rates of 0.1 and 10 s -1 , using electron backscatter diffraction and transmission electron microscopy. The hybrid modeling method utilizes a combination of empirical, physically-based, and neuro-fuzzy models. The flow stress is described as a function of the applied variables of strain rate and temperature using an empirical model. The recrystallization behavior is predicted from the measured microstructural state variables of internal dislocation density, subgrain size, and misorientation between subgrains using a physically-based model. The texture evolution is modeled using artificial neural networks.

Thermodynamic dislocation theory of adiabatic shear banding in steel

“…There, the thermal conductivity is large enough that heat generation can be neglected and no appreciable thermal softening occurs. However, typical stress-strain curves such as the ones shown for aluminum and steel in [11,12] and discussed by us in [6] exhibit thermal softening at large strain rates even without undergoing ASB. When ASB does occur, temperatures within the bands may increase by hundreds of degrees or more, and the thermal forces become one of the principal driving mechanisms.…”

Thermodynamic dislocation theory for non-uniform plastic deformations

“…Only one fitting parameter is required to get the full agreement with the experiment conducted by Follansbee and Kocks (1998) over a wide range of temperatures and strain rates. The theory has been extended to include the interaction between two subsystems by Langer (2017) and used to simulate the stress-strain curves for aluminum and steel which exhibit the thermal softening (Le et al, 2017) in full agreement with the experiments conducted in (Shi et al, 1997;Abbod et al, 2007).…”

Thermodynamic dislocation theory of high-temperature deformation in aluminum and steel

“…Our purpose here is to explore use of the thermodynamic dislocation theory [1][2][3][4][5] in modelling deformations of materials undergoing thermomechanical processing. We look at two sets of high-temperature compression tests, one by Shi et al for aluminum [6], and another by Abbod et al for a steel alloy [7]. By making stress-strain measurements over a range of substantially different temperatures and strain rates, and fitting their results to conventional phenomenological formulas, these investigators provided guidance for practical applications in materials processing.…”

“…III, we show the data for pure aluminum [6], describe our methods for using that data to determine the material-specific parameters, and describe our theoretical interpretation of those measurements. These analyses are extended to the steel data [7] in Sec. IV.…”