Triple junctions (TJs), essential components linking neighboring grain boundaries (GBs), are of great significance for the deformation of entire GB networks in polycrystalline materials. However, kinetic behaviors of TJs and their coupling with GB plasticity remain largely unexplored, especially at atomic scale. Using atomistic in situ nanomechanical testing, we reveal a regime of dynamic TJ reconstruction for accommodating the coordinated deformation of GB network in gold and platinum polycrystals, proceeding through different modes of structural transformations, including disordered atomic arrangement, subgrain, dense stacking faults, and nanotwins. Such TJ reconstruction preferentially nucleates at TJs predicted with strong dragging effect, which serves as an effective route to facilitate the cooperative motion of neighboring GBs, in contrast to the widely-believed TJ deformation in steady state. This reconstruction-coordinated TJ kinetics provides novel insights into complicated GB network evolution and calls for a revisit of TJ roles in polycrystalline materials.

中文翻译：

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应力驱动的三结重建促进了协同晶界变形


三结 （TJ） 是连接相邻晶界 （GB） 的基本组成部分，对于多晶材料中整个 GB 网络的变形具有重要意义。然而，TJs 的动力学行为及其与 GB 塑性的耦合在很大程度上仍未得到探索，尤其是在原子尺度上。使用原子原位纳米力学测试，我们揭示了一种动态 TJ 重建机制，用于适应金和铂多晶中 GB 网络的协调变形，通过不同的结构转变模式进行，包括无序原子排列、亚晶粒、密集堆叠故障和纳米孪生。这种 TJ 重建优先在预测的具有强拖动效应的 TJs 上成核，与人们普遍认为的稳态 TJ 变形相反，这是促进相邻 GB 协同运动的有效途径。这种重建协调的 TJ 动力学为复杂的 GB 网络演变提供了新的见解，并呼吁重新审视 TJ 在多晶材料中的作用。