Specimen- and grain-size dependence of compression deformation behavior in nanocrystalline copper
Specimen- and grain-size dependence of compression deformation behavior in nanocrystalline copper
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DOI：
10.1016/j.ijplas.2013.12.003
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发表时间：
2014-05
影响因子：
9.8
通讯作者：
N. Okamoto;Daisuke Kashioka;T. Hirato;H. Inui
中科院分区：
文献类型：
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作者：
N. Okamoto;Daisuke Kashioka;T. Hirato;H. Inui
研究了平均晶粒尺寸（d）为360、100和34 nm的电沉积纳米晶铜柱的压缩变形行为与试样尺寸（D）的关系。纳米晶柱与d = 360和100 nm的屈服应力不依赖于试样的大小，表现出基本上的体积屈服应力，直到试样的大小被减小到临界值（（D/d）λ = 35和85），低于该值的屈服应力随试样的大小的减小而减小。相比之下，屈服应力与d = 34 nm的纳米晶柱不依赖于试样尺寸，表现出体积屈服应力值为所有试样尺寸的调查。主要的变形机制的变化，从位错滑移的支柱与d = 360和100 nm的晶界扩散蠕变与d = 34 nm的支柱。晶粒尺寸引起的软化发生的支柱与d = 34 nm的变形机制的变化的发生是一致的，而体积屈服应力的支柱与d = 360和100 nm的晶粒尺寸的减小而增加，根据经典的Hall-Petch关系。确定的临界（D/d）的纳米晶铜柱与d = 360和100 nm的值随晶粒尺寸的减小而增加，以便符合粗晶粒铜多晶获得相同的幂律缩放。这是第一个迹象表明，试样尺寸引起的软化从微米级延伸到纳米级，只要占主导地位的变形机制是位错滑移。相当大的临界（D/d）的纳米晶铜柱与d = 360和100 nm的确定的ε值进行了讨论，在相邻的晶粒之间的应变连续性和几何必要的位错的生成，以保持应变连续性的晶界。
The compression deformation behavior of electrodeposited nanocrystalline copper pillars with average grain sizes (d) of 360, 100, and 34 nm has been investigated as a function of specimen size (D). The yield stress for nanocrystalline pillars withd= 360 and 100 nm does not depend on specimen size, exhibiting essentially the bulk yield stress until the specimen size is reduced down to the critical values ((D/d)∗= 35 and 85), below which the yield stress decreases with the decrease in specimen size. In contrast, the yield stress for nanocrystalline pillars withd= 34 nm does not depend much on specimen size, exhibiting the bulk yield stress value for all specimen sizes investigated. The dominant deformation mechanism changes from dislocation glide for pillars withd= 360 and 100 nm to grain boundary diffusional creep for pillars withd= 34 nm. Grain-size induced softening occurs for pillars withd= 34 nm being consistent with the occurrence of change in deformation mechanisms, whereas the bulk yield stress for pillars withd= 360 and 100 nm increases with the decrease in grain size according to the classical Hall–Petch relationship. The critical (D/d)∗values determined for nanocrystalline Cu pillars withd= 360 and 100 nm increases with the decrease in grain size so as to conform to the same power law scaling obtained for coarse-grained Cu polycrystals. This is the first indication that the specimen size-induced softening extends from micrometer to nanometer scales as far as the dominant deformation mechanism is dislocation glide. The considerably large critical (D/d)∗values determined for nanocrystalline Cu pillars withd= 360 and 100 nm are discussed in terms of strain continuity among neighboring grains and the generation of geometrically necessary dislocations to maintain strain continuity at the grain boundaries.