Evolution of grain refinement degree induced by dynamic recrystallization for Nimonic 80A during hot compression process and its FEM analysis

Abstract

In order to analyze the evolution of grain size for Nimonic 80A and further controlling the structures and properties of hot deformed parts, a series of isothermal hot compression tests were conducted with the height reduction range of 10%–60% under the strain rate range of 0.01–10 s−1 and the temperature range of 1237–1523 K on a Gleeble-3500 thermo-mechanical physical simulator. According to the experimental data, the grain refinement degree was proposed and computed in this work so as to quantitatively analyze the variation of grain size during the whole deformation for Nimonic 80A. The onset strains of DRX initiation (εc) were identified by θ−σ curves (strain hardening rates curves) and their derivative. Then the dynamic recrystallization kinetics model and the dynamic recrystallization grain size model were established based on the results from thermo-simulation experiments and metallographic analysis. After that, the grain refinement degrees of the specimens were proposed and calculated, then the effects of temperature, strain rate and deformation degree on the grain refinement degree were discussed through the metallographs over a wide range of temperatures and strain rates. Finally, the developed models were applied in the finite element simulation model, which implies a good application prospect of the theoretical calculation.