The development of alloys with excellent strength-ductility synergy is a long-lasting research theme for material scientists, which also holds true for the newly emerged complex-concentrated alloys (CCAs). Here, a heterogeneously-grained microstructure consisting of recrystallized ultrafine and fine grains containing dense nano-sized L1₂ precipitates, which provides synergic strengthening effects, was intentionally introduced into a Co-free CCA through appropriate thermomechanical processing strategy. This CCA exhibits an ultra-high yield strength of 1.5 GPa, a tensile strength of 1.8 GPa and a remarkable uniform elongation of 18.2% at room temperature. During deformation, dislocation-slip is prevalent in fine grains while stacking faults and nanotwins are activated in ultrafine grains. In particular, strain partition takes place and hetero-deformation-induced (HDI) stress is accumulated via pile-ups of massive dislocations at grain boundaries and domain boundaries between fine grain domains and ultrafine grain domains during straining, resulting in significant HDI hardening. This HDI hardening along with the interaction between multiple deformation modes offers the outstanding strain-hardening ability, delaying the onset of necking and hence enabling high strength and good ductility of alloy. Our results indicate that coupling nanoprecipitates with the fully recrystallized heterogeneous grains is an effective strategy to achieve CCAs with advanced strength-ductility balance.

开发具有优异强度-塑性协同作用的合金是材料科学家长期研究的主题，对于新出现的复合浓缩合金 (CCA) 也是如此。在这里，由再结晶的超细晶粒和含有致密纳米级 L1 _{2的细晶粒组成的异质晶粒微结构}通过适当的热机械加工策略，有意将提供协同强化效果的沉淀物引入到无钴 CCA 中。这种CCA在室温下表现出1.5 GPa的超高屈服强度、1.8 GPa的拉伸强度和18.2%的显着均匀伸长率。在变形过程中，位错滑移在细晶粒中普遍存在，而堆垛层错和纳米孪晶在超细晶粒中被激活。特别是，在应变过程中，通过晶界处的大量位错和细晶粒域与超细晶粒域之间的域边界堆积，发生应变分配，异形变形诱导 (HDI) 应力累积，导致显着的 HDI 硬化。这种 HDI 硬化以及多种变形模式之间的相互作用提供了出色的应变硬化能力，延迟了颈缩的发生，从而使合金具有高强度和良好的延展性。我们的结果表明，将纳米析出物与完全再结晶的异质晶粒耦合是实现具有先进强度-延展性平衡的 CCA 的有效策略。