Collective Dislocation Behavior in Single Crystalline Aluminum Under Indentation
Collective Dislocation Behavior in Single Crystalline Aluminum Under Indentation
复制标题
单晶铝压痕下的集体位错行为
DOI：
10.1007/978-94-017-0483-0_16
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
T. Tsuru
中科院分区：
文献类型：
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作者：
Y. Shibutani;A. Koyama;T. Tsuru
最近导致机械变形具有尺度依赖性的介观实验产生了应变梯度塑性[1]，并进一步激发了离散缺陷动力学方法与连续塑性研究之间的联系[2]。特别是，纳米压痕已被认为是量化特征长度的最合适的材料测试[3]。利用可控的μN级压痕载荷和纳米级位移分辨率，可以精确监测极端局部应力应变场的力学响应。在延性材料中观察到的显微硬度增加的原因被认为是由于在压痕下延伸的集体位错行为[4]。事实上，根据兼容性要求，从表面发出的几何必要位错（GN位错）的密度与应变梯度相关[5]，并且可以很容易地想象出压痕下方的高密度位错区域[6]。然而，仍然没有人提及位错聚集体如何在不均匀应力分布下动态演化并导致尺度相关硬化机制的物理过程，该机制原则上可能基于位错的迁移率。
Recent mesoscale experiments resulting in scale-dependency on the mechanical deformation have yielded the strain-gradient plasticity [1] and furthermore motivated the linkage between the discrete defects dynamics methodology and the continuous plasticity studies [2]. Especially, nanoindentation has been recognized as the most appropriate material testing to quantify the characteristic length [3]. Taking advantage of the controllable µN-level indent load and the nanometer-level displacement resolution, it can accurately monitor the mechanical response of the extremely localized stress and strain field. The reason of increase of microhardness observed in the ductile materials has been thought to be due to collective dislocation behavior extending under the indentation [4]. In fact, the density of the geometrically-necessary dislocation (GN dislocation) emitted from the surface is related to the strain gradient by compatibility requirements [5] and one can easily imagine the high density region of dislocation just beneath the indentation [6]. However, no one still refers the physical process of how the aggregate of dislocations dynamically evolves under the nonuniform stress distribution and leads to the scale-dependent hardening mechanism which may, in principle, be based on the mobility of the dislocations.