FCC-structured CoCrFeMnNi high entropy alloy (HEA) has attracted abroad interests for years because of its excellent mechanical properties, except for strength. Recent experiments have reported a kind of nano-laminated dual-phase (NLDP) FCC/HCP structure that can strengthen the HEA. However, it is still unknown why the HEA can be strengthened by this kind of NLDP structure. Here, we employ molecular dynamics simulations to study the atomistic strengthening mechanism of the NLDP HEA. Dislocation-assisted multiple plastic deformation mechanisms in both FCC and HCP single phase HEAs are observed, and amorphization is also found in the plasticity of HCP phase, which are consistent with the previous experimental characterizations. The HCP phase possesses higher strength because of its higher stacking fault energy, higher Peierls–Nabarro stress and less active dislocation slip systems. It is also found that the introduction of HCP phase can enhance the mechanical properties, including yield stress, yield strain and plastic flow stress, of the NLDP HEAs, which also show volume fraction dependence. And the phase boundary plays crucial roles in the deformation and strengthening of the NLDP HEAs. The plastic deformation of the NLDP HEAs can be divided into two stages, i.e. stage I (plasticity only appears in FCC lamella) and stage II (plasticity in both FCC and HCP lamellas). With the increase of volume fraction, the lamella thickness of FCC matrix phase decreases, leading to continuous strengthening of yield properties and flow stress of stage I because of suppressed dislocation nucleation and confined dislocation motion in FCC matrix phase by the phase boundary. While there is no monotonous relationship between the flow stresses of stage II and the increasing volume fraction of HCP phase, which can be attributed to the competitive mechanisms between strengthening effect of phase boundary on the dislocation motion in FCC phase and softening effect of phase boundary on the dislocation motion in HCP phase. The results should be helpful for understanding the underlying physical mechanism of strengthening of HEAs with NLDP structure.

FCC 结构的 CoCrFeMnNi 高熵合金 (HEA) 多年来以其优异的机械性能（强度除外）引起了国外的兴趣。最近的实验报道了一种可以增强 HEA 的纳米层压双相 (NLDP) FCC/HCP 结构。但是，为什么这种NLDP结构可以加强HEA，目前还不得而知。在这里，我们采用分子动力学模拟来研究 NLDP HEA 的原子强化机制。在 FCC 和 HCP 单相 HEAs 中都观察到位错辅助的多重塑性变形机制，并且在 HCP 相的塑性中也发现了非晶化，这与之前的实验表征一致。HCP 相由于其较高的堆垛层错能而具有较高的强度，较高的 Peierls-Nabarro 应力和较不活跃的位错滑移系统。还发现 HCP 相的引入可以提高 NLDP HEAs 的力学性能，包括屈服应力、屈服应变和塑性流动应力，这些性能也表现出体积分数依赖性。相界在 NLDP HEA 的变形和强化中起着至关重要的作用。NLDP HEA 的塑性变形可分为两个阶段，即阶段 I（塑性仅出现在 FCC 薄片中）和阶段 II（塑性在 FCC 和 HCP 薄片中出现）。随着体积分数的增加，FCC基体相的片层厚度减小，由于相界抑制了 FCC 基体相中的位错形核和受限位错运动，导致阶段 I 的屈服特性和流动应力不断增强。而第二阶段的流动应力与 HCP 相体积分数的增加之间没有单调关系，这可以归因于相界对 FCC 相中位错运动的强化作用和相界对 FCC 相的软化作用之间的竞争机制。 HCP 相中的位错运动。结果应该有助于理解具有 NLDP 结构的 HEA 增强的潜在物理机制。这可以归因于相界对 FCC 相中位错运动的强化作用与相界对 HCP 相中位错运动的软化作用之间的竞争机制。结果应该有助于理解具有 NLDP 结构的 HEA 增强的潜在物理机制。这可以归因于相界对 FCC 相中位错运动的强化作用与相界对 HCP 相中位错运动的软化作用之间的竞争机制。结果应该有助于理解具有 NLDP 结构的 HEA 增强的潜在物理机制。