Micromechanical characterization of grain boundary slip: Towards a deformation mechanism map

晶界滑移的微观力学表征：走向变形机制图

• 批准号: 500076185
• 负责人: Professor Dr. Christoph Kirchlechner
• 金额: --
• 依托单位: School of Materials Engineering
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/500076185?language=en
• 关键词: Micromechanical; characterization; grain; boundary; slip

Grain boundary sliding (GBS) is one key deformation mechanism of polycrystalline materials, particularly for nanocrystalline materials and materials at elevated service temperatures. The immense number of different grain boundaries being present in polycrystalline materials as well as the occurrence of other slip mechanisms (e.g. dislocation slip) prevented a quantitative understanding of the fundamental processes during GBS so far. During the last decade, high temperature nanomechanical testing on focused ion beam (FIB) milled structures was established, and potentially allows for the isolation, characterization and quantification of GBS of one single grain boundary at the micron scale today. It is our objective to use small scale mechanical testing inside a scanning electron microscope (SEM) in order to decouple GBS from other mechanisms of plastic deformation. We propose to measure the shear stress vs. shear strain curve for GBS on individual grain boundaries located in micron and sub-micron sized compression pillars. The grain boundaries will be inclined by 45° with respect to the pillar loading axes. The shear stress is calculated using the applied load as well as the slip geometry (area and inclination of the boundary, direction of slip). The shear strain will be calculated from SEM images, analyzed by digital image correlation (DIC). As soon as a protocol for measuring the shear stress vs. shear strain curve of a GB is established, we will quantitatively assess the GBS mechanisms with regard to the subsequent fundamental questions: 1. What is the activation energy of GBS? 2. Is there an intrinsic size effect in Rachinger-type GBS? 3. What is the influence of grain boundary type for GBS? 4. What is the strain rate dependence on GBS quantitatively? 5. What is the importance of GBS for maintaining compatibility in (macro) polycrystals?

晶界滑动（GBS）是多晶材料，尤其是纳米晶材料和高温材料的一种重要变形机制。在多晶材料中存在大量不同的晶界，以及其他滑移机制（如位错滑移）的发生，迄今为止阻碍了对GBS基本过程的定量理解。在过去的十年中，建立了聚焦离子束（FIB）研磨结构的高温纳米力学测试，并有可能在今天的微米尺度上分离、表征和定量单一晶界的GBS。我们的目标是在扫描电子显微镜（SEM）内进行小规模的力学测试，以便将GBS与其他塑性变形机制解耦。我们建议测量位于微米和亚微米尺寸压缩柱的单个晶界上的GBS的剪切应力-剪切应变曲线。晶界将相对于矿柱加载轴倾斜45°。剪切应力是利用施加的载荷以及滑移几何（边界的面积和倾斜度，滑移方向）来计算的。剪切应变将由扫描电镜图像计算，并通过数字图像相关（DIC）进行分析。一旦建立了GB的剪切应力-剪切应变曲线的测量方案，我们将定量地评估GBS机制，并考虑随后的基本问题：1。GBS的活化能是多少？2. rachinger型GBS是否存在内在的大小效应？3. 晶界类型对GBS的影响是什么？4. 应变率对GBS的定量依赖是什么？5. GBS对于维持（宏观）多晶的相容性有何重要性？