Correlating the atomisitic nature of grain boundary phase transformations to their macroscopic kinetic properties

本提案旨在将金属晶界结构转变的原子起源与它们对输运性质的影响联系起来。其目的是建立对纯金属晶界中温度诱导的晶界相变以及杂质偏析引起的晶界相变及其对界面性质的直接影响的基本理解。用像差校正的透射电子显微镜在原子尺度上研究晶界的结构和相变，用示踪扩散实验研究晶界的宏观输运性质。实验结果将得到选定界面的结构和扩散的原子模拟的系统支持。研究了偏析诱导的晶界转变及其对动力学性质的影响。定义的[001]倾斜晶界将通过块状双晶生长获得，允许根据需要定制晶向偏差和晶界倾斜度。这也使得从原子级到微米长度级的刻度特性成为可能。得到的铜晶界将在受控条件下与Ag、Co和Zr掺杂，先进的透射电子显微镜解决了它们的温度相关结构、偏析和相变。通过示踪剂扩散实验对相同的晶界进行了探测，以确定其与倾斜轴平行和垂直的动力学性质。此外，还将探讨晶界倾斜度偏差对晶界转变及其输运性质的影响，以建立对晶界转变对界面性质影响的整体理解。

The present proposal aims to correlate the atomistic origins of structural transformations at metallic grain boundaries with their impact on the transport properties. The goal is to establish a fundamental understanding of temperature-induced grain boundary phase transformations in pure metallic grain boundaries, as well as those induced by impurity segregation, and their direct impact on interfacial properties. The structure and transitions of grain boundaries will be explored at the atomic scale by aberration-corrected transmission electron microscopy (TEM) and their macroscopic transport properties will be probed by tracer diffusion experiments. The experimental results will systematically be supported by atomistic simulations of structure and diffusion of selected interfaces. Segregation-induced grain boundary transitions and their effect on the kinetic properties will be explored in the systems Cu-Ag, Cu-Co and Cu-Zr. Defined [001] tilt grain boundaries will be obtained by bulk bi-crystal growth, allowing to tailor grain misorientation and grain boundary inclination on demand. This also enables the scale bridging characterization from the atomic level to µm length-scales. The obtained Cu grain boundaries will be doped under controlled conditions with Ag, Co and Zr and advanced TEM resolves their temperature dependent structure, segregation and transitions. The same grain boundaries are probed by tracer diffusion experiments to determine their kinetic properties parallel and perpendicular to the tilt axis. Furthermore, the impact of deviations in grain boundary inclination on grain boundary transitions and their transport properties will also be explored to establish a holistic understanding of the impact of grain boundary transformations on interfacial properties.