Heterogeneous laminated structure (HLS) design offers new opportunities to enhance the mechanical performance of high-entropy alloys (HEAs) through synergistic effects from heterogeneity. However, it remains challenging to introduce the HLS into HEAs via severe plastic deformation due to their strong work-hardening capacity. In this study, a specially designed multi-level HLS, characterized by alternatively stacked micro-grained soft CoCrFeNi layers and nanostructured ultra-hard Al_0.3CoCrFeNi layers containing a three-phase microstructure (composed of nanograined face-centered cubic matrix, (Al, Ni)-rich B2 precipitates, and Cr-rich σ precipitates), is controllably introduced into FCC HEAs via a conventional thermo–mechanical processing involving hot-pressing, cold-rolling, and annealing. Meanwhile, thermo–mechanical processing induces Al element diffusion across the layer interface, resulting in the formation of an interfacial transition layer and the establishment of a strong interface bonding between the neighboring CoCrFeNi and Al_0.3CoCrFeNi layers. As a result, the multi-level HLSed CoCrFeNi/Al_0.3CoCrFeNi composite exhibits a yield strength as high as 1127±25.4 MPa while maintaining a large fracture elongation (up to (26.3±2.4)%). Such an excellent strength–ductility synergy surpasses that of most previously reported high-performance monolithic bulk CoCrFeNi and Al_0.3CoCrFeNi HEAs prepared through careful chemical composition optimization and/or thermo–mechanical processing. Strong hetero-deformation induced strengthening benefited from the apparent microstructural/microhardness difference and the strong interface bonding between the neighbouring CoCrFeNi and Al_0.3CoCrFeNi layers, together with simultaneous activation of multiple strain hardening mechanisms containing mechanical twinning, stacking faults and precipitation strengthening, is responsible for the excellent strength–ductility combination. This multi-level HLS and its fabrication strategy provide an enlightening way to develop strong and ductile HEAs and can also be applied to high-performance designs of other metallic materials.

中文翻译：

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通过高熵合金的异质层状结构设计提高强度和延展性协同作用


异质层状结构 （HLS） 设计为通过异质性的协同效应提高高熵合金 （HEA） 的机械性能提供了新的机会。然而，由于其强大的加工硬化能力，通过严重的塑性变形将 HLS 引入高熵合金仍然具有挑战性。在本研究中，一种专门设计的多级 HLS，其特征是交替堆叠的微晶软 CoCrFeNi 层和纳米结构的超硬 Al_0.3CoCrFeNi 层，其中包含三相微观结构（由纳米晶面心立方基体、（Al，Ni）富 B2 沉淀物和富 Cr σ沉淀物组成），通过涉及热压的常规热机械加工可控地引入 FCC HEA， 冷轧和退火。同时，热机械加工诱导 Al 元素在层界面上扩散，从而形成界面过渡层，并在相邻的 CoCrFeNi 和 Al_0.3CoCrFeNi 层之间建立牢固的界面键合。因此，多级HLSed CoCrFeNi/Al_0.3CoCrFeNi复合材料表现出高达1127±25.4 MPa的屈服强度，同时保持较大的断裂伸长率（高达（26.3±2.4）%）。这种出色的强度-延展性协同作用超过了以前报道的大多数高性能整体体 CoCrFeNi 和 Al_0.3CoCrFeNi HEAs，这些高熵合金是通过仔细的化学成分优化和/或热机械加工制备的。强烈的异质变形诱导的强化得益于明显的微观结构/显微硬度差异以及相邻的 CoCrFeNi 和 Al 0 之间的强界面结合_。3个 CoCrFeNi 层，以及同时激活包含机械孪晶、堆叠故障和沉淀强化的多个应变硬化机制，是实现出色的强度-延展性组合的原因。这种多级 HLS 及其制造策略为开发坚固且具有延展性的 HEA 提供了一种启发性的方法，也可以应用于其他金属材料的高性能设计。