Mechanically Driven Grain Boundary Formation in Nickel Nanowires
Mechanically Driven Grain Boundary Formation in Nickel Nanowires
复制标题
镍纳米线中机械驱动的晶界形成
DOI：
10.1021/acsnano.7b06605
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发表时间：
2017
期刊：
影响因子：
17.1
通讯作者：
Han Xiaodong
中科院分区：
文献类型：
--
作者：
Wang Lihua;Kong Deli;Zhang Yin;Xiao Lirong;Lu Yan;Chen Zhigang;Zhang Ze;Zou Jin;Zhu Ting;Han Xiaodong
金属纳米材料广泛应用于微纳器件中。然而，这些纳米材料中机械驱动的微观结构演变尚不清楚，特别是当存在大的应力和应变梯度时。在这里，我们报告了使用高分辨率透射电子显微镜对含有纳米级双片层的镍纳米线进行的原位弯曲实验。我们发现，镍纳米线的大的局部弯曲变形最初导致了小角度倾斜晶界（GB）的形成，该晶界由扩散GB层中随机分布的位错组成。进一步弯曲加剧了局部塑性变形，从而导致晶界区域局部晶域的严重扭曲和塌陷，从而将小角度晶界转变为高角度晶界。原子模拟与原位原子尺度成像相结合，揭示了弯曲引起的应变梯度的作用以及GB形成中相关的几何必要位错。这些结果为理解金属纳米材料通过晶界形成而机械驱动的微观结构变化提供了有价值的理解。这项工作对于细化大块纳米晶体材料中的晶粒也具有重要意义。
Metallic nanomaterials are widely used in micro/nanodevices. However, the mechanically driven microstructure evolution in these nanomaterials is not clearly understood, particularly when large stress and strain gradients are present. Here, we report thein situbending experiment of Ni nanowires containing nanoscale twin lamellae using high-resolution transmission electron microscopy. We found that the large, localized bending deformation of Ni nanowires initially resulted in the formation of a low-angle tilt grain boundary (GB), consisting of randomly distributed dislocations in a diffuse GB layer. Further bending intensified the local plastic deformation and thus led to the severe distortion and collapse of local lattice domains in the GB region, thereby transforming a low-angle GB to a high-angle GB. Atomistic simulations, coupled within situatomic-scale imaging, unravelled the roles of bending-induced strain gradients and associated geometrically necessary dislocations in GB formation. These results offer a valuable understanding of the mechanically driven microstructure changes in metallic nanomaterials through GB formation. The work also has implications for refining the grains in bulk nanocrystalline materials.