Developing metallic materials with ultra-high strength and sufficient ductility, while retaining good work-hardening ability has always been a relentless pursuit. Architecting of heterogeneous microstructure ushers in a new way to achieve this goal. Hierarchical precipitation and partial recrystallization are two commonly used approaches to obtain heterogeneous microstructure. In this work, a dual heterogeneous microstructure was designed thorough combining partial recrystallization with hierarchical precipitation aiming to obtain high strength and ductile alloy with sufficient work hardening ability. The newly-developed VCoNi1.2Al0.2 medium entropy alloy (MEA) with dual heterogeneous microstructure exhibits ultra-high strength while retaining sufficient ductility (σYS,σUTS and ductility are 1857 MPa, 2191 MPa, 9.8 % for the sample annealed at 800 ℃, and 1461 MPa, 1934 MPa, 22.3 % for the sample annealed at 900 ℃, respectively), which is superior than most reported MEAs and high entropy alloys (HEAs). Such excellent mechanical properties in this work are attributed to the dual heterogeneous microstructure, which endows alloy with multiple strengthening mechanisms, and the strengthening mechanisms can be adjusted by controlling the microstructures. The uniform distribution of nano precipitated phase and partial recrystallized region not only enhances the crack tolerance ability, but also improves the dislocation storage capability, and prolongs strain hardening. This work offers more possibilities for the development of high-strength and ductile structural materials with sufficient work-hardening ability.

中文翻译：

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具有双重异质微观结构的超强延展性中等熵合金


开发具有超高强度和足够延展性的金属材料，同时保持良好的加工硬化能力一直是我们不懈追求的目标。异构微结构的架构为实现这一目标开辟了一条新道路。分层沉淀和部分重结晶是获得异质微观结构的两种常用方法。本工作通过局部再结晶与分级沉淀相结合，设计了一种双重异质微观组织，旨在获得具有足够加工硬化能力的高强度和延展性合金。新开发的具有双重异质微观结构的 VCoNi1.2Al0.2 中等熵合金 （MEA） 在保持足够延展性的同时表现出超高强度（在 800 °C 退火的样品中，σYS、σUTS 和延展性分别为 1857 MPa、2191 MPa，9.8 %，在 900 °C 下退火的样品分别为 1461 MPa、1934 MPa，22.3 %），优于大多数报道的 MEA 和高熵合金 （HEA）。这项工作中如此优异的力学性能归因于双重异质微观组织，它赋予合金多种强化机制，并且可以通过控制微观组织来调整强化机制。纳米析出相和部分再结晶区的均匀分布不仅增强了抗裂能力，而且提高了位错存储能力，延长了应变硬化时间。这项工作为开发具有足够加工硬化能力的高强度和延展性结构材料提供了更多的可能性。