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.

众所周知，在远低于玻璃化转变温度的温度下，块体金属玻璃 (BMG) 的塑性变形局限于剪切带内。由此产生的结构变化以及变形玻璃的量热、动力学和机械响应的相关特征已通过事后方法（即在施加的机械应力停止后）进行了彻底分析。然而，到目前为止，剪切带过程中的过程几乎没有被研究过，而且少数可用的（准）原位研究也受到了争议性的讨论。与塑性剪切变形同时进行的初步原位扩散实验表明原子输运异常大幅增强。在类似条件下变形的结晶镍的自扩散没有观察到这种增强。因此，本提案的总体目标是通过基于补充原位和准原位实验的战略方法来揭示控制异常快速原子输运和相关结构修饰的机制。这些分析将为剪切带激活和传播的机制提供深入和新的见解。特别是，我们将解决一些未解决的问题，这些问题对于全面理解 BMG 的变形响应至关重要，例如原子输运速率的异常增强对扩散物质的原子尺寸或变形协议的依赖性。我们将分析传输增强与剪切带内特定化学重新分布或结构变化的相互关系。为此，需要进行放射性示踪剂扩散实验和基于 TEM 的研究。最后，基于专用放射性示踪剂扩散分析和先进结构分析方法的补充方法和专业知识的结合，应以协调一致的方式应用，这将为对大块金属玻璃变形特性的基本理解提供重大进展。