Study of grain-boundary-dislocation interactions by advanced in situ µLaue diffraction

通过先进的原位 µLaue 衍射研究晶界-位错相互作用

基本信息

批准号：
254889688
负责人：
Professor Dr. Christoph Kirchlechner
金额：
--
依托单位：
Max-Planck-Institut für Eisenforschung GmbH (MPIE)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/254889688?language=en
关键词：
Study grain boundary dislocation interactions

项目摘要

The enormous influence of grain boundaries on the plastic deformation behavior of engineering materials has been known for several decades and is of paramount concern for industrial applications worldwide. Nevertheless, up to now no thorough understanding of the interaction processes of single dislocations with different types of grain boundaries exist. Macroscopically these effects are often smeared out due to the infinite number of available dislocation sources and grain-boundaries present in engineering materials. However, in micron sized samples, where the number and size of dislocation sources are limited, few dislocations control the plastic deformation of the entire device. This size effect was intensively studied over the last decade in single crystalline materials and a basic understanding for face-centered-cubic (FCC) materials exists. However, for material structures containing only a few grain-boundaries a thorough understanding is lacking.A size effect of mechanical properties was recently also reported for micron sized bi-crystals. Due to the limited number of dislocation sources, the higher stresses and the shorter diffusion path it is well possible, that the grain-boundary-dislocation interaction processes change at the micron scale. Controlling the grain-boundary parameters and the loading direction allows for an activation of macroscopically unfavored or unidentifiable interaction processes. Thus, bi-crystalline micro compression samples allow for studying grain-boundary-dislocation interaction processes in general, but particularly their size dependency.In the proposed work the mechanical behavior of bi-crystalline, micron sized copper (Cu) samples should be analyzed by advanced diffraction and imaging methods. As a modell system, micromechanical samples containing different grain and twin boundaries will be prepared by focused ion beam milling (FIB) and subsequently tested at the micro Laue endstation of the CRG-IF at BM32 of the ESRF synchrotron source. Main focus of the work is the continuous measurement of distribution and density of geometrical necessary dislocations (GNDs) and elastic strains during the deformation of micron sized pillars by in situ micro Laue (µLaue) diffraction. These data will be correlated to the mechanical data (strength, hardening) globally measured during the experiment. The microLaue experiments will be supported by complementary state of the art methods like transmission electron microscopy (TEM), molecular dynamics (MD) and discrete dislocation dynamics (DDD) simulations. We aim for the understanding of size-dependent bi-crystalline plasticity as well as the quantification and understanding of involved grain-boundary dislocation interaction processes.

晶界对工程材料塑性变形行为的巨大影响已为人所知数十年，并且是全球工业应用的首要关注点。然而，迄今为止，人们对单个位错与不同类型晶粒的相互作用过程还没有透彻的了解。从宏观上看，由于工程材料中存在无限数量的可用位错源和晶界，这些效应常常被掩盖。然而，在微米尺寸的样品中，位错源的数量和尺寸有限，几乎没有位错控制。过去十年来，人们对单晶材料中的这种尺寸效应进行了深入研究，并且对面心立方（FCC）材料有了基本的了解。然而，对于仅包含少量晶界的材料结构。最近还报道了微米级双晶的机械性能的尺寸效应，由于位错源的数量有限，应力较高且扩散路径较短，因此很可能存在晶界。 -错位控制晶界参数和加载方向可以激活宏观上不利或无法识别的相互作用过程，因此，双晶微压缩样品可以研究一般的晶界位错相互作用过程。，但特别是它们的尺寸依赖性。在所提出的工作中，应通过先进的衍射和成像方法来分析双晶、微米级铜 (Cu) 样品的机械行为作为模型系统，包含不同晶粒和孪晶界的微机械样品将通过聚焦离子束铣削 (FIB) 制备，随后在 ESRF 同步加速器源 BM32 的 CRG-IF 微劳厄终端站进行测试。通过原位微劳厄 (μLaue) 衍射分析微米级柱变形过程中几何必要位错 (GND) 和弹性应变的分布和密度。 microLaue 实验将得到透射电子显微镜 (TEM)、分子动力学 (MD) 和离散位错动力学 (DDD) 模拟等补充技术的支持。旨在了解尺寸相关的双晶塑性以及所涉及的晶界位错相互作用过程的量化和理解。