Modelling stress relaxation after hot deformation: Microstructure-property relationships in Nb-bearing steels

Stress relaxation taking place after hot deformation is modelled by incorporating the simultaneous action of various physical phenomena. Dislocation recovery, recrystallization, and precipitation are all interrelated adopting new formulations. Dislocation recovery is approached through a vacancy-mediated dislocation climb approach. Recrystallization is considered to be meta-dynamic or static, and the effects of precipitate pinning and (interstitial and substitutional) solute drag are incorporated. The kinetics of precipitation nucleation, growth, and coarsening are also taken into account; precipitate nucleation in dislocation cells is assumed and thus the dislocation cell evolution is accounted for. The softening behaviour is thus tracked for 6 micro alloyed steel grades and compared with 37 softening curves for a range of temperatures and prior deformation rates; the modelling describes the experiments with great accuracy. The application of the approach to additive manufacturing microstructural relaxation is discussed.

Automated summary

Stress relaxation after hot deformation is modeled by considering various physical phenomena, including dislocation recovery, recrystallization, and precipitation. The model incorporates new formulations, such as a vacancy-mediated dislocation climb approach for dislocation recovery. The softening behavior of 6 microalloyed steel grades is tracked and compared with experimental data. The approach is also discussed for its application in additive manufacturing microstructural relaxation.