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

凹痕引起的塑料带的横截面是单晶硅，并且通过透射电子显微镜（TEM）观察到铝，以便知道它们在凹痕下的内部结构变化。通过聚焦离子束（FIB）技术，将涉及凹入区域的小块从样品中切出并变薄至几百纳米厚度。在硅的情况下，静液压诱导的相位转变恢复到钻石结构，并在卸载后与散装的晶体学方向不同，与已收到的样品进行了重结晶的样品进行了比较。由60度位错和螺钉位错组成的完美位错可能是从相变和钻石大块之间的边界发出的。还通过分子动力学模拟研究了位错的发射和移动机制。另一方面，在情况下发现，在最大剪切应力区域内组织了小于一个微米的亚晶粒铝。由于集体机械行为，这似乎是位错网络的自组织之一。新发现在纳米引起测试的凹痕负载和凹痕深度之间观察到的不稳定位移爆发与脱位测试的关系很大可能与脱位发射有关。在本研究中，通过分子动力学模拟了单晶铝中的脱位发射和棱柱位错环的形成。讨论了三种不同的嵌入原子类型电位的两种不同类型的压痕和原子间描述引起的应力分布的影响。结果，由于缩进器和棱镜位错环的严重损坏的表面原子层发出位位，它们具有相同的滑动方向，但在滑动平面上不存在，它们是由从表面和交叉滑移机构中发出的剪切环之间的不稳定反应连接的。较少的