Atomic transport and structural modifications during shear banding of a bulk metallic glass

大块金属玻璃剪切带过程中的原子输运和结构改性

• 批准号: 531610270
• 负责人: Professor Dr. Sergiy Divinski
• 金额: --
• 依托单位: Institut für Materialphysik
• 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/531610270?language=en
• 关键词: Atomic; transport; structural; modifications; during

At temperatures significantly below the glass transition temperature, plastic deformation of bulk metallic glasses (BMGs) is well known to localise within shear bands. The resulting structural changes as well as related signatures of calorimetric, kinetic and mechanical responses of the deformed glasses have been thoroughly analysed by post-mortem approaches, i.e. after the applied mechanical stress has ceased. However, the processes during shear banding have scarcely been investigated up to now and the few (quasi-) in-situ studies available are controversially discussed. Preliminary in-situ diffusion experiments performed concurrently to plastic shear deformation indicated an abnormally large enhancement of atomic transport. No such enhancement has been observed for self-diffusion of crystalline Ni deformed under similar conditions. The overarching goal of the present proposal is thus to uncover the mechanisms governing the abnormally fast atomic transport and the related structure modifications by a strategic approach based on complementing in-situ and quasi-in-situ experiments. These analyses shall provide deep and new insight into the mechanisms of shear band activation and propagation. In particular, we shall address a number of unresolved problems which are critical for a comprehensive understanding of the deformation response of BMGs, such as a dependence of the abnormal enhancement of atomic transport rates on the atom size of the diffusing species or the deformation protocol. We shall analyze the interrelation of the transport enhancement with specific chemical re-distributions or structural changes within the shear bands. For these purposes, both radiotracer diffusion experiments and TEM-based investigations need to be performed. Finally, it is the combination of complementing methods and expertise based on dedicated radiotracer diffusion analyses and advanced structural analyses methods, which shall be applied in a concerted way, that shall provide significant advances in the basic understanding of deformation properties of bulk metallic glasses.

在高于玻璃过渡温度的温度下，众所周知，散装金属玻璃（BMG）的塑性变形在剪切带中众所周知。通过验尸方法（即应用机械应力停止后）对变形玻璃的量热，动力学和机械响应的相关结构变化以及相关的特征进行了彻底的分析。但是，到目前为止，几乎没有研究剪切带过程中的过程，并且有争议地讨论了少数（准）的原位研究。与塑性剪切变形同时进行的初步原位扩散实验表明原子转运的异常增强。在相似条件下，没有观察到这种增强的结晶Ni自我扩散。因此，本提案的总体目标是揭示有关异常快速原子运输的机制，以及基于补充原位和准式坐姿实验的战略方法的相关结构修改。这些分析应为剪切带激活和传播的机制提供深刻而新的见解。特别是，我们将解决许多未解决的问题，这些问题对于对BMG的变形响应的全面理解至关重要，例如原子传输速率异常增强对散射物种的原子大小或变形方案的依赖。我们将通过特定的化学重新分布或剪切带中的结构变化分析运输增强的相互关系。为了这些目的，需要进行放射性示意剂扩散实验和基于TEM的研究。最后，基于专用的放射性扩散分析和高级结构分析方法的补充方法和专业知识的结合，应以协调的方式应用，在对散装金属眼镜的变形特性的基本理解方面应具有重大进步。