High-entropy alloys have attracted much attention due to their unique microstructures and excellent properties. Since their invention more than ten years ago, research attention has been mainly focused on the study of multicomponent alloys with equiatomic or near-equiatomic compositions. Here we propose a novel design of non-equiatomic medium-entropy alloys that contain one matrix element and several equiatomic alloying elements. To verify the utility of this new design, a series of Co-free Fe_x(CrNiAl)_100-x (at.%, 25 ≤ x ≤ 65) medium-entropy alloys were designed from the much-studied FeNiCrCoAl high-entropy alloy. Detailed characterization reveals that the alloys exhibit novel two-phase microstructures consisting of B2-ordered nanoprecipitates and BCC-disordered matrix. As the alloys deviate far from equiatomic composition, the structure of the nanoprecipitates transfers from a spinodal-like intertwined structure to a nanoparticle dispersed structure. Previous parametric approaches to predict phase formation rules for high-entropy alloys are unable to describe the phase separation behaviors in the studied alloys. Our findings provide a new route to design medium-entropy alloys and also demonstrate a strategy for designing nanostructured alloys from multicomponent alloy systems through simple variations in non-equiatomic compositions.

中文翻译：

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非等原子中熵合金的设计。

高熵合金由于其独特的微观结构和出色的性能而备受关注。自从十多年前发明以来，研究重点主要集中在具有等原子或近等原子组成的多组分合金的研究上。在这里，我们提出了一种新的非等原子中熵合金设计，该合金包含一个基体元素和几个等原子合金元素。为了验证这种新设计的实用性，一系列无钴的Fe _x（CrNiAl）_100-x（at。％，25≤x≤65）中熵合金是由经过广泛研究的FeNiCrCoAl高熵合金设计而成。详细的表征表明，该合金展现出新颖的两相微观结构，包括B2级纳米沉淀和BCC无序基体。当合金偏离等原子组成时，纳米沉淀的结构从类似旋节线的缠绕结构转移到纳米颗粒分散的结构。先前用于预测高熵合金的相形成规则的参数方法无法描述所研究合金的相分离行为。我们的发现为设计中熵合金提供了一条新途径，并且还展示了通过简单地改变非等原子组成从多组分合金系统设计纳米结构合金的策略。