首页> 外文期刊>Philosophical Magazine, A. Physics of condensed matter, defects and mechanical properties >Atomistic computation of the image force on a dislocation in a bicrystal - II. Case of a large difference between the elastic moduli of the two half-crystals
【24h】

Atomistic computation of the image force on a dislocation in a bicrystal - II. Case of a large difference between the elastic moduli of the two half-crystals

机译:双晶中位错上像力的原子计算-II。两个半晶体的弹性模量差异较大的情况

获取原文
获取原文并翻译 | 示例
           

摘要

The behaviour of a dislocation in the vicinity of an interface between two half-crystals having notably different elastic moduli has previously been investigated by a computer simulation by Beauchamp and Lepinoux, who considered two half-crystals with similar elastic coefficients. The two half-crystals have a bcc structure with the same orientation and lattice parameter and are welded along the (100) plane, parallel to the a(0)[001] screw dislocation. Two interatomic potentials representing alpha-iron have been used. Detailed exploration of the Peierls valleys within 4a(0) from the interface has been performed by applying an external stress which balances both the local lattice friction and the long-range image force. It is found that the mean stresses of each valley follow approximately the stress curve determined by Pacheco and Mura on the basis of the continuous Peierls dislocation core, perturbed by the interface. The simulation presents, however, a stress peak which is lower and more extended. Changes in the dislocation core have been observed as the dislocation approaches the interface; in the 'soft' medium the core tends to become slightly narrower, whereas it clearly widens in the 'hard' medium. This is because the effect of the applied stress is uniform throughout each half-crystal whereas the image force is stronger on the parts of the dislocation core close to the interface than on those farther away. Systematic variations in the Peierls valleys amplitudes have been found; when the interface is approached from the 'soft' medium side, the amplitude increases whereas it decreases when approaching from the 'hard' side. The latter decrease is such that Peierls valleys completely disappear near the interface and an unstable zone forms on the 'hard' side. It has been possible to keep dislocations there, but only under a dissociated form compound of two partials having b/2 screw components. The stacking fault created, which is not normally stable in the bcc structure, is of the 'unstable fault' type to which Rice attributes a key role in the dislocation nucleation at a crack tip. [References: 16]
机译:先前已经通过Beauchamp和Lepinoux的计算机模拟研究了两个弹性模量显着不同的半晶体之间的界面附近位错的行为,他们考虑了两个具有相似弹性系数的半晶体。两个半晶体具有相同取向和晶格参数的bcc结构,并沿(100)平面焊接,与a(0)[001]螺钉位错平行。已经使用了代表α-铁的两个原子间电势。通过施加平衡局部晶格摩擦力和远距离图像力的外部应力,已对界面4a(0)内的Peierls谷进行了详细的研究。结果发现,每个山谷的平均应力大致遵循由Pacheco和Mura在界面扰动的连续Peierls位错核心的基础上确定的应力曲线。但是,模拟显示了一个应力峰值,该应力峰值较低且延伸更大。随着位错接近界面,已观察到位错核心发生了变化。在“软”介质中,核心趋向于稍微变窄,而在“硬”介质中则明显变宽。这是因为施加应力的作用在每个半晶体中是均匀的,而位错核心靠近界面的部分的图像力要比远离界面的部分强。已经发现Peierls山谷振幅的系统变化;当从“软”介质侧接近界面时,振幅增大,而从“硬”介质侧接近时振幅减小。后者的减少使得Peierls谷在界面附近完全消失,并且在“硬”侧形成了不稳定区域。可以在此处保持位错,但只能在具有b / 2个螺钉组件的两个部分的分离形式下进行。产生的堆垛层错通常在bcc结构中不稳定,属于“不稳定断层”类型,赖斯将其归因于裂纹尖端位错形核中的关键作用。 [参考:16]

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号