Eutectic high entropy alloys, with lamellar arrangement of solid solution phases, represent a new paradigm for simultaneously achieving high strength and ductility, thereby circumventing this well-known trade-off in conventional alloys. However, dynamic strengthening mechanisms and phase-boundary interactions during external loading remain unclear for these eutectic systems. In this study, small-scale mechanical behavior was evaluated for AlCoCrFeNi_2.1 eutectic high entropy alloy, consisting of a lamellar arrangement of L1₂ and B2 solid-solution phases. The ultimate tensile strength was 1165 MPa with ductility of ~18% and ultimate compressive strength was 1863 MPa with a total compressive fracture strain of ~34%. Dual mode fracture was observed with ductile failure for L1₂ phase and brittle mode for B2 phase. Phase-specific mechanical tests using nano-indentation and micro-pillar compression showed higher hardness and strength and larger strain rate sensitivity for B2 compared with L1₂. Micro-pillars on B2 phase deformed by plastic barreling while L1₂ micro-pillars showed high density of slip steps due to activation of more slip systems and homogenous plastic flow. Mixed micro-pillars containing both the phases exhibited dual yielding behavior while the interface between L1₂ and B2 was well preserved without any sign of separation or cracking. Phase-specific friction analysis revealed higher coefficient of friction for B2 compared to L1₂. These results will pave the way for fundamental understanding of phase-specific contribution to bulk mechanical response of concentrated alloys and help in designing structural materials with high fracture toughness.

共晶高熵合金具有固溶体相的层状排列，代表了同时实现高强度和延展性的新范例，从而规避了传统合金中众所周知的这种权衡。然而，这些共晶系统在外部加载过程中的动态强化机制和相界相互作用仍不清楚。在本研究中，评估了 AlCoCrFeNi _2.1共晶高熵合金的小尺度机械行为，该合金由 L1 ₂和 B2 固溶体相的层状排列组成。极限拉伸强度为 1165 MPa，延展性约为 18%，极限压缩强度为 1863 MPa，总压缩断裂应变约为 34%。观察到双模式断裂，L1 ₂相为延性破坏，B2 相为脆性破坏。使用纳米压痕和微柱压缩的相特定机械测试表明，与 L1 ₂相比，B2 具有更高的硬度和强度以及更大的应变率灵敏度。 B2 相上的微柱因塑性滚转而变形，而 L1 ₂相微柱由于更多滑移系统的激活和均匀塑性流动而表现出高密度的滑移台阶。含有这两种相的混合微柱表现出双重屈服行为，而 L1 ₂和 B2 之间的界面保存完好，没有任何分离或破裂的迹象。特定相摩擦分析表明，与 L1 ₂相比，B2 的摩擦系数更高。这些结果将为从根本上理解相特定对浓缩合金整体机械响应的贡献铺平道路，并有助于设计具有高断裂韧性的结构材料。