In situ visualization of birth and annihilation of grain boundaries in an Au nanocrystal.
In situ visualization of birth and annihilation of grain boundaries in an Au nanocrystal.
复制标题
DOI：
10.1103/physrevlett.109.225501
复制
发表时间：
2012-11
影响因子：
8.6
通讯作者：
He Zheng;Jianbo Wang;J. Huang;A. Cao;S. Mao
中科院分区：
文献类型：
--
作者：
He Zheng;Jianbo Wang;J. Huang;A. Cao;S. Mao
用高分辨透射电镜原位观察了纳米Au在拉伸和释放应力过程中小角度晶界的形成和消失过程。在离轴拉伸载荷（耦合单轴拉伸和弯曲应力）下，完全位错的成核导致Au单晶内部形成15°的小角度晶界。令人惊讶的是，位错被完全消灭，伴随着消失的GB后，外部应力的去除，表明塑性弯曲是可恢复的，在蠕变。背力和表面应力在这种伪弹性行为中起着重要的作用。这种瞬时GB动力学无法在异地实验研究中捕获。纳米晶体中的这种伪弹性弯曲变形将对具有微弯曲能力的纳米机械器件的设计产生重要影响。
The formation and vanishing processes of a low angle grain boundary (GB) in nanosized Au during tension and release of stress, respectively, were obsvered by in situ high resolution transmission electron microscopy. The nucleation of perfect dislocations led to the formation of a 15° low angle GB inside an Au nanocrystal upon off-axial tensile loading (coupled uniaxial tensile and bending stress). Strikingly, the dislocations were completely annihilated accompanied with the disappearance of the GB after the removal of external stress, indicating that plastic bending is recoverable in the nanocrystal. The back force and surface stress played important roles in such a pseudoelastic behavior. This transient GB dynamics cannot be captured in ex situ experimental investigations. Such pseudoelastic bending deformation in nanosized crystals will have an important impact on the designing of nanomechanical devices with ultrahigh bending capability.