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异质和均质塑性变形之间的转变。到目前为止，尽管这种转变对于基础研究和玻璃应用具有重要意义，但人们对这种转变知之甚少。为了解决控制这一转变的潜在基本机制，我们设计了一种协调一致的策略，其中包括紧密相连的实验和理论分析：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，可以评估基本和实际重要性的主要物理参数。这些结果将与理论预测进行比较，与从离散状态到连续状态的整个过渡状态和不同长度尺度的流变特性有关。该方法依赖并利用联盟成员的互补专业知识，并应提供控制变形局部化和均匀流动之间过渡的机制的物理实体图。仅基于一些实验研究，文献中最近的建议将这种转变与热依赖和时间依赖的结构重排之间的竞争联系起来。这些专注于特定成分的研究表明，变形模式的剧烈变化可能是玻璃内部发生基本机制转变的足迹。预计它会受到不同结构变化的控制，特别是中程有序（MRO）的性质和长度规模及其动态。到目前为止，这方面尚未被了解。 MEGALO 项目的目标是研究这种转变并确定控制它的一阶特征。因此，选择了两种金属玻璃，在金属玻璃可用的范围内，它们在易碎性方面表现出相当明显的特征。将在压缩和拉伸方面进行高温测试，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函数的应变局部化问题。变形样品将被表征，以识别发生应变局部化的区域和这些区域之外的区域之间的结构变化。为此，将使用互补的实验技术，即波动 TEM、扩散率测量和纳米压痕，与通过分子动力学和有限元计算对金属玻璃中的应变局部化进行建模。参与小组的密切合作以及博士生的交流将确保 MEGALO 项目规模桥接方法的成功。