One of key factors in designing high-performance alloys is to understand their incipient behavior. To get detailed real-time atomic scale evolutions of multi-principal element alloys (MPEAs) during nanoindentation incipient yielding, molecular dynamics (MD) simulations were carried out. Emphases are given to the effects of lattice distortion (LD) and chemical short-range ordering (CSRO) on the initiation of plasticity in body-centered cubic (BCC) MPEAs. The initial plastic mechanism is embryo nucleation assisted and the incipient behavior is strongly affected by LD and CSRO. Specifically, the embryo nucleation load P_e is reduced by LD and CSRO and the incipient drop P₀ is lowered by LDI that only comes from atomic size difference and further declined by CSRO. This is because LD and CSRO could boost embryo nucleation, which can act as precursors for dislocation nucleation. This is consistent with the free-end nudged elastic band observations. Although P_e is weakened by LDII generated by introducing extra elements, P₀ is intensified because severe LD could dominate the following process. The dislocation starvation mechanism is found in an average-atom (AA) model. However, it is replaced by dislocation interactions due to LD and CSRO. Density functional theory (DFT) calculations suggest that charge density distribution and the amount of directional Al-Al bonding would play a critical role in the onset of plastic deformation. When a larger indenter radius was used in MD simulations, the dislocation starvation mechanism is absent in AA model due to the reduced maximum shear stress. Instead, the dislocation propagation prevails. With respect to the orientation effect, three investigated orientations demonstrate a distinct yielding behavior.

设计高性能合金的关键因素之一是了解它们的初始行为。为了详细了解多主元素合金 (MPEA) 在纳米压痕初期屈服过程中的实时原子尺度演变，进行了分子动力学 (MD) 模拟。重点是晶格畸变 (LD) 和化学短程有序 (CSRO) 对体心立方 (BCC) MPEA 塑性起始的影响。初始塑性机制是胚胎成核辅助的，初期行为受 LD 和 CSRO 的强烈影响。具体来说， LD 和 CSRO 降低了胚胎成核负荷P _e ，并且初始下降P ₀被仅来自原子大小差异的 LDI 降低，并被 CSRO 进一步降低。这是因为 LD 和 CSRO 可以促进胚胎成核，这可以作为位错成核的前体。这与自由端轻推弹性带观察结果一致。虽然P _e被引入额外元素产生的 LDII 削弱，但P ₀加剧，因为严重的 LD 可能主导以下过程。在平均原子 (AA) 模型中发现了位错饥饿机制。然而，由于 LD 和 CSRO，它被位错相互作用所取代。密度泛函理论 (DFT) 计算表明电荷密度分布和定向 Al-Al 键合量将在塑性变形开始时发挥关键作用。当在 MD 模拟中使用较大的压头半径时，由于最大剪应力降低，AA 模型中不存在位错饥饿机制。相反，位错传播占优势。关于取向效应，三个研究的取向表现出明显的屈服行为。