1] Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA [2] Department of Materials Science and Engineering and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China.
Nat Commun. 2013;4:2340. doi: 10.1038/ncomms3340.
Stacking fault tetrahedra, the three-dimensional crystalline defects bounded by stacking faults and stair-rod dislocations, are often observed in quenched or irradiated face-centred cubic metals and alloys. All of the stacking fault tetrahedra experimentally observed to date are believed to originate from vacancies. Here we report, in contrast to the classical vacancy-originated ones, a new kind of stacking fault tetrahedra formed via the interaction and cross-slip of partial dislocations in gold nanocrystals. The complete atomic-scale processes of nucleation, migration and annihilation of the dislocation-originated stacking fault tetrahedra are revealed by in situ high-resolution observations and molecular dynamics simulations. The dislocation-originated stacking fault tetrahedra can undergo migration and annihilation due to mechanical loading in a manner that is not expected in bulk samples. These results uncover a unique deformation mechanism via dislocation interaction inside the confined volume of nanocrystals and have important implications regarding the size effect on the mechanical behaviour of small-volume materials.
堆垛层错四面体是由堆垛层错和梯状位错限定的三维晶体缺陷，常存在于淬火或辐照的面心立方金属和合金中。迄今为止，所有实验观察到的堆垛层错四面体都被认为是由空位形成的。相比之下，我们报告了一种新的堆垛层错四面体，它是通过金纳米晶体中部分位错的相互作用和交叉滑移形成的。通过原位高分辨率观察和分子动力学模拟，揭示了位错起源的堆垛层错四面体的成核、迁移和湮灭的完整原子尺度过程。由于机械加载，位错起源的堆垛层错四面体可以发生迁移和湮灭，这在体样品中是不期望的。这些结果揭示了受限于纳米晶体体积内部位错相互作用的一种独特变形机制，并对小体积材料的力学行为的尺寸效应具有重要意义。
