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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.

几十年来，晶界对工程材料塑性变形行为的巨大影响一直是人们所熟知的，并且是世界范围内工业应用的首要关注点。然而，迄今为止，还没有对单个位错与不同类型晶界的相互作用过程有透彻的了解。宏观上，由于工程材料中存在无限数量的位错源和晶界，这些效应常常被掩盖。然而，在微米尺寸的样品中，其中位错源的数量和尺寸是有限的，很少的位错控制整个装置的塑性变形。在过去的十年中，这种尺寸效应在单晶材料中得到了深入的研究，并且对面心立方（FCC）材料有了基本的了解。然而，对于只有少量晶界的材料结构，还缺乏深入的了解。最近也报道了微米尺寸双晶的力学性能的尺寸效应。由于位错源的数量有限，更高的应力和更短的扩散路径，很可能，晶粒-晶界-位错相互作用过程在微米尺度上发生变化。控制晶界参数和加载方向允许激活宏观上不利的或不可识别的相互作用过程。因此，双晶微压缩样品一般允许研究晶界位错相互作用过程，但特别是它们的尺寸dependency.In所提出的工作中的双晶，微米尺寸的铜（Cu）样品的力学行为应分析先进的衍射和成像方法。作为一个模型系统，包含不同的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，并随后在ESRF同步辐射源的BM 32 CRG-IF的微劳厄终端站进行测试。工作的主要重点是通过原位微劳厄（μ劳厄）衍射连续测量微米尺寸柱体变形过程中几何必要位错（GNDs）和弹性应变的分布和密度。这些数据将与在实验期间整体测量的机械数据（强度、硬化）相关联。微劳厄实验将得到补充的最先进的方法，如透射电子显微镜（TEM），分子动力学（MD）和离散位错动力学（DDD）模拟的支持。我们的目标是了解尺寸相关的双晶塑性以及量化和了解所涉及的晶界位错相互作用过程。