Abstract In this work, a novel non-equiamotic Ni47.5Cr23.75Co23.75Ti5 medium-entropy alloy strengthened by heterogeneous precipitates was successfully fabricated. Our results demonstrate heterogeneous precipitation behaviors, i.e. nanosized spherical particles with L12 superlattice in inner grains plus nano-lamellar precipitates with long-period stacking ordered structure nearby grain boundaries, could bring out outstanding strength-ductility synergy properties. This heterogeneous precipitation-strengthened medium-entropy alloy exhibits high yield strength and ultimate tensile strength of ~840 MPa and ~1220 MPa, respectively, and remains an excellent ductility of ~34.8%. Further analyses indicate this heterogeneous precipitation result in effective precipitation-strengthening enhancement (~603 MPa), stacking-faults activated in spherical precipitates region and deformation nanotwins induced in lamellar precipitates region synergy contribute to high work-hardening capacity and ductility. Our work provides not only a useful insight of precipitation behaviors caused by Ti element addition in non-equiatomic high/medium-entropy alloys, but also a further understanding of precipitation-strengthening in high/medium-entropy alloys.

中文翻译：

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非等原子中等熵合金中的非均相沉淀促进了优异的机械性能

摘要 在这项工作中，成功地制备了一种新型非均相Ni47.5Cr23.75Co23.75Ti5 非均相沉淀强化的中熵合金。我们的结果证明了异质沉淀行为，即内部晶粒中具有 L12 超晶格的纳米球状颗粒加上在晶界附近具有长周期堆叠有序结构的纳米层状沉淀物，可以带来出色的强度-延展协同性能。这种异质沉淀强化的中熵合金分别具有~840 MPa 和~1220 MPa 的高屈服强度和极限抗拉强度，并保持~34.8% 的优异延展性。进一步的分析表明，这种非均质沉淀导致有效的沉淀强化增强（~603 MPa），在球形沉淀区激活的堆叠故障和在层状沉淀区引起的变形纳米孪晶协同作用有助于提高加工硬化能力和延展性。我们的工作不仅提供了对非等原子高/中熵合金中 Ti 元素添加引起的沉淀行为的有用见解，而且还提供了对高/中熵合金中沉淀强化的进一步理解。