Advanced Modeling and Microstructural Insights into the Hot Deformation Behavior of Fe–11Al–5Mn–1Nb–1C Low-Density Steel

Abstract

The hot deformation behavior of Fe–11Al–5Mn–1Nb–1C low-density steel was investigated using a GLEEBLE 3800R thermomechanical simulator across a temperature range of 900–1200 ℃ and strain rates of 1–0.001 s−1. An Arrhenius-type constitutive model was developed to predict flow stress during deformation, alongside a bilayer evolutionary neural network (EvoNN) model based on an artificial neural network (ANN) approach. The EvoNN model demonstrated higher prediction accuracy than the constitutive model. Microstructural analysis revealed a ferritic matrix with kappa carbide as a secondary phase at 900 and 1000 ℃, while at 1100 and 1200 ℃, a dual-phase structure (ferrite + austenite) with fine kappa carbides at the phase interface was observed. NbC particles were consistently present in all hot compressed samples. Partial dynamic recrystallization (DRX) occurred at 900 and 1000 ℃, whereas more extensive DRX was observed at 1100 and 1200 ℃. Grain coarsening was evident at lower strain rates, increasing as the strain rate decreased. Fine NbC particles and kappa carbides pinned grain boundaries, potentially delaying DRX onset, while coarse NbC particles appeared to enhance particle-stimulated nucleation (PSN), introducing complexity to DRX dynamics and contributing to model discrepancies in the constitutive and EvoNN model.