Metallic glasses and strain localization

金属玻璃和应变定位

• 批准号: 505731929
• 负责人: Professor Dr. Jürgen Horbach
• 金额: --
• 依托单位: Lehrstuhl II: Weiche Materie
• 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/505731929?language=en
• 关键词: Metallic; glasses; strain; localization

The focus of the MEGALO project is set by the transition between heterogeneous and homogeneous plastic deformation of metallic glasses. So far, this transition is poorly understood even though it has important bearings for basic research as well as glass application. In order to address the underlying basic mechanisms that control this transition, a well-concerted strategy has been devised that consists of closely interlinked experimental and theoretical analyses: structural heterogeneities and their impact will be studied on different length scales, starting at the local scale, through complementing experimental techniques, allowing an evaluation of the main physical parameters of fundamental as well as practical importance. These results will be compared with theoretical predictions, in connection with rheological properties all the way through the transition regime and at various length scales, from the discrete to the continuum regime. This approach relies on and exploits the complementing expertise of the members of the consortium and shall provide a physically solid picture of the mechanisms that govern the transition between localization of deformation and homogeneous flow. Based on only a few experimental studies, recent suggestions in the literature linked the transition to the competition between thermal- and time-dependent structural rearrangements. These few studies, focusing on specific compositions, suggest that the drastic change of the deformation mode would be a footprint of a transition in the elementary mechanisms occurring inside the glass. It is expected to be governed by different structural changes and particularly by the nature and the length scale of the medium range order (MRO) as well as its dynamics. So far, this aspect has not yet been understood. It is the aim of MEGALO project to investigate this transition and to identify what are the first order features that control it. For this reason, two metallic glasses are selected that show, within the range available for metallic glasses, rather distinct characteristics concerning their fragility. High temperature testing will be performed in both compression and tension and a particular attention will be paid to develop appropriate Digital Image Correlation (DIC) techniques to tackle strain localisation as a function of temperature and strain rate in SEM environment. The deformed samples will be characterised to identify structural variations between zones where strain localisation occurs and outside these zones. To this end, complementary experimental techniques, namely fluctuation TEM, diffusivity measurements and nanoindentation, will be used in combination with the modelling of strain localisation in metallic glasses via molecular dynamics and finite element calculations. The close collaboration of the participating groups as well as the exchange of PhD students shall ensure the success of the scale-bridging approach of the MEGALO project.

MEGALO项目的重点是金属玻璃的非均匀塑性变形和非均匀塑性变形之间的过渡。到目前为止，人们对这种转变知之甚少，尽管它对基础研究和玻璃应用具有重要意义。为了解决控制这种转变的潜在基本机制，已经设计了一个协调一致的策略，由紧密相连的实验和理论分析组成：结构异质性及其影响将在不同的长度尺度上进行研究，从局部尺度开始，通过补充实验技术，允许对基本和实际重要性的主要物理参数进行评估。这些结果将与理论预测进行比较，与从离散到连续的各种长度尺度的过渡制度和流变性质有关。这种方法依赖并利用了联盟成员的互补专业知识，并将提供控制变形局部化和均匀流动之间过渡的机制的物理可靠图像。仅基于少数实验研究，最近的文献建议将这种转变与热相关和时间相关的结构重排之间的竞争联系起来。这些研究集中在特定的成分上，表明变形模式的剧烈变化可能是玻璃内部发生的基本机制转变的足迹。预计它将受到不同结构变化的支配，特别是受到中程秩序（MRO）的性质和长度尺度及其动力学的支配。到目前为止，这方面还没有被理解。MEGALO项目的目的是研究这种转变，并确定控制它的首要特征是什么。因此，我们选择了两种金属玻璃，这两种金属玻璃在金属玻璃的可用范围内，在脆弱性方面表现出相当明显的特征。高温测试将在压缩和拉伸下进行，并将特别注意开发适当的数字图像相关（DIC）技术，以解决SEM环境中温度和应变率的函数应变定位问题。将对变形样品进行表征，以确定应变局部化发生的区域之间和这些区域之外的结构变化。为此，互补的实验技术，即波动透射电镜、扩散率测量和纳米压痕，将通过分子动力学和有限元计算与金属玻璃应变局部化建模相结合。参与小组的密切合作以及博士生的交流将确保MEGALO项目的规模衔接方法取得成功。