Integrated experimental and 3D cellular automaton study of dynamic recrystallization mechanism in 42CrMo steel

To systematically investigate the dynamic recrystallization (DRX) behavior of 42CrMo steel during hot deformation, we established an integrated framework that combines physics-based modeling, experimental characterization, and numerical simulation. A physics-driven DRX kinetics model—built on the Zener–Hollomon (Z) parameter, Kocks–Mecking dislocation-density evolution, and a modified Avrami equation—was calibrated with multiple sets of isothermal compression tests, and its predictions agree closely with the measurements. Comprehensive experiments show that deformation temperature, strain rate, and strain act synergistically to control grain and microstructural evolution; microscopy further confirms that discontinuous DRX (DDRX), characterized by grain-boundary bulging and necklace-type nucleation, is the predominant softening mechanism, while the martensite packet–block size after quenching scales linearly with the prior-austenite grain size. A three-dimensional cellular automaton (3D CA) model, which incorporates grain-boundary migration driven by dislocation-density gradients together with a Moore-26 neighborhood rule, successfully reproduces heterogeneous nucleation and topological grain evolution; the simulated DRX volume fractions and grain-size distributions match the experimental results closely. This integrated framework fully reveals the DRX mechanism of 42CrMo steel and provides a solid theoretical basis for optimizing the hot-forging parameters of large 42CrMo components.