Beryllium as a fast diffuser in bulk metallic glasses

由于大块非晶合金在实验可及的时间尺度上对过冷液态晶化是稳定的，因此现在有可能验证金属系统中玻璃化转变和过冷液体的各种模型以及分子动力学模拟。这些理论与粘性、扩散系数等宏观物理量以及它们与温度的关系有关。本项目旨在研究7Be作为一种小而快速的元素在大块非晶合金Zr46.7Ti8.3Cu7.5Ni10Be27.5和Pd40Ni10Cu30P20中的玻璃化转变附近和过冷态的扩散，以阐明基本的扩散机制。对于Zr46.7Ti8.3Cu7.5Ni10Be27.5，将重点放在温度依赖关系上，并与已发表的互扩散数据进行比较，以研究化学和热力学因素的影响。特别是令人惊讶的事实是，在调查的温度范围内，钴的扩散速度快于铍的扩散速度，这一事实将得到深入的研究。示踪剂注入应有助于避开氧化问题，并允许在不同的静水压力下进行实验。不同的压力依赖关系表明不同的扩散机制。对于更稳定的Pd40Ni10Cu30P20玻璃，应该有可能将研究扩展到过冷液体，以检验最近关于热玻璃化转变温度和熔化温度之间的温度区间内扩散机制变化的理论。

Since the discovery of bulk amorphous alloys, which are stable against crystallization in the undercooled liquid state on experimental accessible time scales, it is now possible to verify the various models of the glass transition and the undercooled liquid as well as molecular dynamics simulations in metallic systems. These theories are connected to macroscopic quantities like viscosity and diffusivity and their temperature dependence. Within this project it is intended to investigate the diffusion of 7Be as a small and therefore very fast element in the bulk amorphous alloy Zr46.7Ti8.3Cu7.5Ni10Be27.5 and Pd40Ni10Cu30P20 near the glass transition and in the supercooled state to elucidate the basic diffusion mechanism. For Zr46.7Ti8.3Cu7.5Ni10Be27.5 emphasis will be put on the temperature dependence and comparison with already published data on interdiffusion should allow to study influences of chemistry and the thermodynamic factor. In particular the surprising fact, that in the investigated temperature range the Co diffuses faster than the Be will be investigated thouroghly. Tracer implantation should help to circumvent oxidation problems and allow experiments under various hydrostatic pressures. Different pressure dependencies are indicative of different diffusion mechanisms. For the more stable Pd40Ni10Cu30P20 glass it should be possible to extend the investigations to supercooled liquid to test recent theories about the change of the diffusion mechanism in the temperature interval between the caloric glass transition temperature and the melting temperature.