Crystalline materials can be strengthened by introducing dissimilar phases that impede dislocation glide. At the same time, the changes in microstructure and chemistry usually make the materials less ductile. One way to circumvent the strength–ductility dilemma is to take advantage of heterogeneous nanophases which simultaneously serve as dislocation barriers and sources. Owing to their superior mechanical properties, heterogeneous nanostructured materials (HNMs) have attracted a lot of attention worldwide. Nevertheless, it has been difficult to characterize dislocation dynamics in HNMs using classical continuum models, mainly due to the challenges in describing the elastic and plastic heterogeneity among the phases. In this work, we advance a phase-field dislocation dynamics (PFDD) model to treat multi-phase materials, consisting of phases differing in composition, structural order, and size in the same system. We then apply the advanced PFDD model to exploring two important but divergent materials design problems in HNMs: dislocation/obstacle interactions and dislocation/interface interactions. Results show that the interactions between a dislocation and distribution of obstacles varying in structure and composition cannot be understood by simply interpolating from their individual interactions with a dislocation. It is also found that materials containing interfaces with nanoscale thicknesses and compositional gradients have a much higher dislocation bypass stress than those with sharp interfaces, providing an explanation for the simultaneous high strength and toughness of thick interface-containing nanolaminates as observed in recent experiments.

可以通过引入阻止位错滑动的不同相来强化结晶材料。同时，微观结构和化学成分的变化通常会使材料的延展性降低。避免强度-延展性困境的一种方法是利用同时作为位错屏障和来源的异质纳米相。异质纳米结构材料（HNMs）由于其优越的力学性能在世界范围内引起了广泛的关注。然而，很难使用经典的连续模型来描述 HNM 中的位错动力学，这主要是由于在描述相间的弹性和塑性异质性方面存在挑战。在这项工作中，我们提出了一种相场位错动力学 (PFDD) 模型来处理多相材料，由在同一系统中组成、结构顺序和大小不同的相组成。然后，我们应用先进的 PFDD 模型来探索 HNM 中两个重要但不同的材料设计问题：位错/障碍相互作用和位错/界面相互作用。结果表明，位错与结构和组成不同的障碍物分布之间的相互作用不能通过简单地从它们与位错的相互作用中插值来理解。还发现包含具有纳米级厚度和成分梯度的界面的材料比具有尖锐界面的材料具有更高的位错旁路应力，这为最近实验中观察到的含有厚界面的纳米层压材料同时具有高强度和韧性提供了解释。