Size-induced weakening and grain boundary-assisted deformation in 60 nm grained Ni nanopillars
Size-induced weakening and grain boundary-assisted deformation in 60 nm grained Ni nanopillars
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DOI：
10.1016/j.scriptamat.2010.09.010
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发表时间：
2011-01-01
影响因子：
6
通讯作者：
Greer, Julia R.
中科院分区：
文献类型：
--
作者：
Jang, Dongchan;Greer, Julia R.
纳米晶金属通常具有较高的强度和良好的抗疲劳性能，其强度与晶粒尺寸成反比，呈平方根依赖性，直至晶粒尺寸类似于20 nm，这代表了众所周知的Hall-Petch关系。我们发现，在亚微米尺寸的表面主导结构中，如纳米柱，60 nm晶粒的Ni-W合金的抗拉强度随着柱直径的减小而降低；此外，在直径大于100 nm的矿柱中，变形机制出现了由位错驱动的变形向100 nm及以下矿柱中晶界介导的变形过渡，包括晶粒旋转和晶界迁移；我们假设自由表面的存在激活了这些晶界介导的变形过程，晶粒尺寸比之前观察到的要大得多，导致达到的强度更低(C) 2010 Acta Materialia Inc .出版，Elsevier Ltd版权所有
Nanocrystalline metals generally exhibit high strengths and good fatigue resistance Their strengthening scales with the inverse of grain size through square root dependence down to grain sizes of similar to 20 nm, representing the well-known Hall-Petch relation Here we show that in surface-dominated structures with sub-micron dimensions, i e nanopillars, 60 nm grained Ni-W alloys exhibit lower tensile strengths with decreasing pillar diameter, form shear bands and undergo mechanical twinning Moreover, there appears to be a transition in the deformation mechanism from dislocation-driven deformation in pillars with diameters larger than 100 nm to grain-boundary mediated deformation in pillars of 100 nm and below, including grain rotation and grain-boundary migration, processes previously observed only in grain sizes below 20 nm in materials of the same composition We postulate that the presence of free surfaces activates these grain-boundary mediated deformation processes at much larger grain sizes than observed before and results in lower attained strengths (C) 2010 Acta Materialia Inc Published by Elsevier Ltd All rights reserved