A gradient dislocation-structured low-carbon steel with enhanced strength-ductility synergy

Abstract

Usually, the improvement of strength of structural materials is at the cost of ductility. Here, a superior synergy of high strength (σy ~ 526.8–582.6 MPa) and ductility (εf ~ 25.5–19.3%) is achieved in the gradient dislocation-structured low-carbon steel subjected to torsion deformation, which is much better than that (σy ~ 317.9 MPa and εf ~ 22.8%) of its coarse-grained counterpart. The enhanced strength is attributed to the back stress, grain refinement and the introduction of numerous dislocations (i.e., work hardening) whose density increases consistently with the radius along from the core to the surface. The high ductility results from the promising work hardening capacity of the gradient dislocation-structure. This study provides a practical route to developing advanced structural materials with enhanced integrated mechanical properties.