Abstract Although many high-entropy alloys (HEAs) possess excellent mechanical properties, they are not exempt from the common dilemma of strength–ductility trade-off in most cases, which limits their potential applications. Herein, rotationally accelerated shot peening was used to introduce different gradient hierarchical microstructures, including gradients in twin and dislocation densities, and hierarchical nanotwin, into a CoCrFeNiMn HEA by adjusting the processing parameters. The resulting gradient structures and their effect on hardening behaviour and mechanical properties were systematically explored. Quantitative analysis indicates that deformation twinning, including hierarchical nanotwinning could be more important than dislocation slip in terms of their contribution to hardness and strain hardening capability, depending on the gradient structure profile. It was found that simultaneous improvement of strength and ductility can be achieved in a gradient structure with a thin deformed layer and an undeformed core. Based on our experimental results, we propose that a gradient structure with a largest possible strength difference between the surface layer and the undeformed core would maximize the strength–ductility synergy.

中文翻译：

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通过梯度分级显微组织同时提高高熵合金的强度和延展性

摘要 尽管许多高熵合金 (HEAs) 具有优异的机械性能，但在大多数情况下，它们都无法摆脱强度-延展性权衡的常见困境，这限制了其潜在应用。在此，旋转加速喷丸硬化用于通过调整加工参数将不同的梯度分级微观结构（包括孪晶和位错密度梯度以及分级纳米孪晶）引入 CoCrFeNiMn HEA。系统地研究了由此产生的梯度结构及其对硬化行为和机械性能的影响。定量分析表明，就其对硬度和应变硬化能力的贡献而言，变形孪生，包括分层纳米孪生可能比位错滑移更重要，取决于梯度结构剖面。发现在具有薄变形层和未变形芯的梯度结构中可以实现强度和延展性的同时提高。根据我们的实验结果，我们提出在表面层和未变形的核心之间具有最大可能强度差异的梯度结构将最大化强度-延展性协同作用。