Atomic-scale dynamic process of deformation-induced stacking fault tetrahedra in gold nanocrystals
JW Wang and S Narayanan and JY Huang and Z Zhang and T Zhu and SX Mao, NATURE COMMUNICATIONS, 4, 2340 (2013).
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.
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