Speaker
Description
Designing thermomechanical processing routes requires accurate control of microstructure evolution across sequential deformation and heat-treatment steps. In this work, we present a physics-based model that continuously predicts the microstructural evolution of AA6082 throughout complex thermomechanical histories. A key feature of the model is its ability to carry forward the microstructure from one processing step to the next, such that the state after deformation serves as the initial condition for subsequent processing, such as heat treatments.
We describe microstructure evolution during plastic deformation using a continuous dynamic recrystallization framework that tracks dislocation density, grain and subgrain sizes, boundary misorientation distributions, and grain boundary fractions. We couple these internal variables with constitutive equations to predict flow stress as a function of strain, strain rate, and temperature. After deformation, the stored energy coming from dislocation accumulation drives restoration processes during the subsequent heat treatment.
To validate the model, we performed compression tests on cylindrical samples at temperatures between 25 °C and 450 °C, strain rates from 0.1 s⁻¹ to 1900 s⁻¹, and varying strains. We then applied controlled heating to the solution heat treatment temperature at rates between 1 and 20 K/min. We characterized the resulting microstructures using EBSD and used both flow curves and microstructural data to calibrate the model.
The model captures key features of the material response, including strong initial strain hardening due to dislocation pileups and the subsequent evolution during restoration. We show that the recrystallization occurs already during heating, and that the start temperature increases with heating rate, while remaining largely insensitive to deformation rate for the lower deformation temperatures. The results highlight the competing roles of recovery in the static recrystallization and demonstrate the capability of the model to predict microstructure evolution continuously across thermomechanical processing steps.