Mechanism of dynamic recrystallization behavior in low-alloy steel during vibration-assisted hot forming

Conventional hot forming of low-alloy steel is often constrained by die friction and non-uniform plastic flow, leading to distinct end, bulging, and core zones with marked differences in dynamic recrystallization (DRX), grain size, and microstructural uniformity. This study proposes a low-frequency, high-amplitude mechanical vibration-assisted hot-forming method to regulate global plastic flow and microstructural evolution. Unlike previous studies focused mainly on ultrasonic vibration-induced surface or volume effects, this work combines zone-specific electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) characterization with macroscopic finite-element and crystal-plasticity simulations to clarify how mechanical vibration controls deformation zoning and regional DRX behavior. Vibration produces a synergistic effect of “friction reduction, flow promotion, and stress diversion,” reducing the peak forming load by approximately 28.5%, weakening conventional deformation zoning, activating deformation in the end zone, promoting strain and stress redistribution, and reducing grain-size differences among zones. In the core zone, the DRX area fraction increases from 16.01% to 24.16%, while the average grain size decreases from 1.99 to 1.62 μm. The enhanced DRX is associated with increased resolved shear stresses on multiple slip systems, dislocation accumulation and rearrangement, subgrain formation, and high-angle grain boundary development. These findings provide a mechanistic basis for producing low-alloy steel components with more uniform and refined microstructures and support potential applications in high-performance gears, bearings, and load-bearing structures. © 2026. Published by Elsevier B.V.