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Collective Mechanical Behavior of dislocation Network Developed under Indentation

压痕下位错网络的集体力学行为

基本信息

批准号：
13450047
负责人：
SHIBUTANI Yoji
金额：
$ 9.15万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

Cross sections of the indent-induced plastic zones is single crystalline silicon and aluminum are observed by the transmission electron microscopy (TEM) in order to know their internal structural changes under indentation. A tiny piece involving the indented region is cut from the sample and thinned until a few hundred nanometer thickness by means of the Focus Ion Beam (FIB) technique. At the case of silicon, the hydrostatic pressure-induced phase transition recovers to the diamond structure with the different crystallographic orientation from the bulk after unloading, being compared with the sample having received the heat treatment for recrystallization. Perfect dislocations consisting of the 60 degree dislocations and screw dislocations may be emitted from the boundary between the phase transition and the diamond bulk. Emission and movemeat mechanism of the dislocation are also investigated with help of the molecular dynamics simulations. On the other hand, it is found at the case o … More f single crystalline aluminum that the subgrains less than one micron are organized at the maximum shear stress region. It seems to be one of the self-organization of dislocation network as a result of the collective mechanical behaviors.New finding of unstable displacement burst observed in the relation between the indent load and indent depth of a nanoindentation test is much possible to be related to dislocation emission. In the present research, the dislocation emission and the prismatic dislocation loop formation in a single crystalline aluminum are simulated by the molecular dynamics. Effects of the stress distribution due to two different types of indenters and of the interatomic description by three different embedded atom type potentials are discussed with much emphasis. At a result, the dislocations are emitted from the severely damaged surface atomic layer due to the indenter and the prismatic dislocation loops, which have the same gliding direction but not on the glide plane, are attained by unstable reaction between the shear loops emitted from the surface and cross slip mechanism. Less

通过透射电子显微镜（TEM）观察压痕引起的塑性区的横截面为单晶硅和铝，以了解它们在压痕作用下的内部结构变化。从样品上切下包含凹痕区域的一小块，并通过聚焦离子束 (FIB) 技术将其减薄至几百纳米的厚度。在硅的情况下，与接受再结晶热处理的样品相比，在卸载后，静水压力诱导的相变恢复为具有与块体不同的晶体取向的金刚石结构。由 60 度位错和螺旋位错组成的完美位错可以从相变和金刚石块体之间的边界发射。还借助分子动力学模拟研究了位错的发射和移动机制。另一方面，在单晶铝的情况下发现，小于一微米的亚晶粒组织在最大剪切应力区域。这似乎是集体力学行为导致的位错网络自组织之一。在纳米压痕测试的压痕载荷和压痕深度之间的关系中观察到的不稳定位移爆发的新发现很可能与位错发射有关。在本研究中，通过分子动力学模拟单晶铝中的位错发射和棱柱位错环的形成。重点讨论了两种不同类型压头对应力分布的影响以及三种不同嵌入原子类型势对原子间描述的影响。结果，由于压头的作用，位错从严重受损的表面原子层中发射出来，并且通过表面发射的剪切环与交叉滑移机制之间的不稳定反应获得具有相同滑移方向但不在滑移面上的棱柱形位错环。较少的