Ultrasonic nanocrystal surface modification (UNSM) treatment on non-equiatomic medium- and high-entropy alloy (HEA) of Fe_x(CoCrMnNi)_100-x is firstly introduced and its impact on microstructure and mechanical properties are revealed. By UNSM, severe plastic deformation-induced dislocation and deformation twins (DTs) arise at the topmost surface. Especially, Fe₆₀(CoCrMnNi)₄₀ (Fe60), which is classified as a medium-entropy alloy (MEA), exhibits ε-martensitic transformation. In the room temperature tensile test, a high strength of ∼600 MPa and ductility of ∼65 % elongation (strain to failure) is accomplished in Fe60. Initially formed DTs and ε-martensitic transformation by UNSM treatment plays a key role in retardation of necking point via both twinning-induced plasticity and transformation-induced plasticity. However, Fe₂₀(CoCrMnNi)₈₀ (Fe20) comparatively shows low strength of ∼550 MPa and ∼40 % elongation, owing to the low accommodation of DTs than Fe60. Our research will provide new guidelines for enhancing the mechanical properties of MEA and HEA.

首先介绍了对Fe _x（CoCrMnNi）_{100- x的}非等原子中高熵合金（HEA）进行超声纳米晶表面改性（UNSM）的方法，并揭示了其对组织和力学性能的影响。通过UNSM，最塑性变形引起的位错和形变孪晶（DT）出现在最表面。特别是Fe ₆₀（CoCrMnNi）₄₀被分类为中熵合金（MEA）的（Fe60）具有ε马氏体转变。在室温拉伸试验中，在Fe60中实现了约600 MPa的高强度和约65％的延展性（断裂应变）。通过孪晶诱导的可塑性和相变诱导的可塑性，通过UNSM处理最初形成的DTs和ε-马氏体转变在颈缩点延迟中起关键作用。但是，由于DTs的容纳量低于Fe60，因此Fe ₂₀（CoCrMnNi）₈₀（Fe20）的强度相对较低，约为550 MPa，延伸率约为40％。我们的研究将为增强MEA和HEA的机械性能提供新指导。