Abstract Enhancing strength-ductility synergy of materials has always been a hot but difficult topic in material science, for most structural materials, steels in particular, it is inevitable to sacrifice ductility when increasing strength, and vice versa. In this study, by introducing a linear gradient in grain size into Fe-Mn-C twinning-induced plasticity (TWIP) steel, which is one of the promising structural steels in automobile industry, it is interesting to find that a simultaneous improvement of strength and plasticity (SISP) has been successfully achieved. It is believed that this evasion of strength-ductility trade-off may be mainly attributed to the formation of geometric necessary dislocations during tensile deformation, which contributes to an additional work-hardening especially in the later deformation. Such extraordinary strain hardening, which is inherent to the gradient structures and is absent in homogeneous materials, helps enhance the strength and delay the necking. This represents a novel strategy for the strength-ductility improvement which emphasizes the importance of work hardening and thickness of gradient layer (not a narrow sharp gradient) in material design. Inspired by this, other methods on optimizing structural design of the high-performance materials may be developed.

中文翻译：

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同时提高强度和塑性：梯度微观结构的附加加工硬化

摘要 增强材料的强度-塑性协同作用一直是材料科学中的热点但难点的课题，对于大多数结构材料，特别是钢材，在提高强度的同时，不可避免地要牺牲塑性，反之亦然。在这项研究中，通过将晶粒尺寸的线性梯度引入 Fe-Mn-C 孪生诱导塑性 (TWIP) 钢，这是一种在汽车工业中很有前途的结构钢，有趣的是发现强度的同时提高和可塑性 (SISP) 已成功实现。据信，这种强度-延展性权衡的规避可能主要归因于拉伸变形期间几何必要位错的形成，这有助于额外的加工硬化，尤其是在后期变形中。这种特殊的应变硬化是梯度结构所固有的，在均质材料中不存在，有助于提高强度并延迟颈缩。这代表了一种提高强度-延展性的新策略，它强调了材料设计中加工硬化和梯度层厚度（不是窄的陡峭梯度）的重要性。受此启发，可以开发其他优化高性能材料结构设计的方法。