Simultaneous improvement of strength and uniform elongation of ferrite-bainite steel with heterogeneous networked microstructure

A novel heterogeneous networked dual-phase structure, composed of bainite grains surrounding the ferrite grains and forming a networked structure, was successfully introduced into the low-carbon ferrite-bainite steel through a two-step heat treatment process. The ferrite-bainite steel with the networked structure exhibited a high ultimate tensile strength of 872 ± 39 MPa, a good uniform elongation of 15.59 %, and a high total elongation of 22.79 %. Meanwhile, it possessed excellent work hardening behaviors compared to the ferrite-bainite steel with an island feature. The improvement of the comprehensive mechanical properties was attributed to the influence of hetero deformation induced (HDI) hardening and the synergistic deformation of the dual-phase structure.