In this paper, various gradient structures (i.e., the ferrite grain size increases continuously with the depth) with different grain size distributions are produced in low-carbon steel by using pre-torsion deformation and thermal annealing at ~ 550 °C to 700 °C for 0.5 h. Results indicate that the grain size distribution possesses a crucial influence on mechanical properties of gradient-structured samples. The yield strength decreases steady accompanied by a gradual increase in uniform ductility and static toughness with increasing the ferrite grain size. The optimal synergy of high yield strength (σ_y~ 506.0 ± 3.9 MPa), promising uniform ductility (ε_u~ 9.6 ± 0.5%) and static toughness (U_r~ 108.8 ± 4.1 MJ/m³) is achieved by a specific gradient structure with the grain size distribution from ~ 7.2 µm at the surface to ~ 16.5 µm at the core, which is much better than that (σ_y~ 318.2 ± 1.6 MPa, ε_u~ 13.4 ± 0.4% and U_r~ 102.5 ± 4.8 MJ/m³) of its coarse-grained (CG) counterpart. Related strengthening and toughening mechanisms are also discussed.

在本文中，通过预扭转变形和〜550°C至700°C的热退火，在低碳钢中产生了具有不同晶粒尺寸分布的各种梯度结构（即，铁素体晶粒尺寸随深度连续增加）。持续0.5小时 结果表明，晶粒度分布对梯度结构样品的力学性能具有至关重要的影响。随着铁素体晶粒尺寸的增加，屈服强度稳定降低，同时均匀延展性和静态韧性逐渐提高。的高屈服强度的最佳协同作用（σ _ý〜506.0±3.9兆帕），有前途的均匀延展性（ε _û〜9.6±0.5％）和静态韧性（û _[R〜108.8±4.1 MJ /米³）由特定的梯度结构具有从〜7.2微米的粒度分布在表面至〜16.5微米的核心，这是更好的比（实现σ _ý〜318.2±1.6兆帕，ε _û〜13.4±0.4％和ü _{- [R}〜102.5±4.8 MJ /米³的粗粒度（CG）对应物）。还讨论了相关的强化和增韧机制。