Superior Strength–Ductility Synergy in Multiheterogeneous Gradient‐Structured Medium Mn Steel

A novel multiheterogeneous gradient structure was successfully fabricated in medium Mn steel via a hybrid process integrating low‐temperature aging, cyclic torsion, and short‐term high‐temperature annealing. This structure exhibits distinct gradient distributions of austenite phase fraction and dislocation density along the macroscopic radial direction of the specimen. Microscopically, austenite grains within each gradient layer display diverse morphological characteristics and size distributions, while ferrite grains contain a high density of nanoscale B2 precipitates. This unique hierarchical architecture enables the sequential activation of the transformation‐induced plasticity (TRIP) effect across the core‐to‐surface gradient layers over a wide strain range. The synergistic interplay of multiple deformation mechanisms, including continuous TRIP effect, sustained heterogeneous deformation‐induced (HDI) strengthening, twinning‐induced plasticity (TWIP) effect in the surface region, and precipitation strengthening, yields an exceptional strength–ductility synergy. Compared with its homogeneous counterpart, the multiheterogeneous gradient structure achieves a ~70% enhancement in yield strength and a ~26% increase in ultimate tensile strength, while retaining excellent ductility of ~41%. These findings provide a promising strategy for developing medium Mn steels with superior strength–ductility balance and offer valuable insights for the design of advanced structural materials in engineering applications.