Deformation Response of Oriented Crystalline Aggregates: Experiment and Theory

这项工作探索了取向晶体材料中的微结构如何将滑移的原子物理中介到更大的宏观强度和延性响应。强度和延展性是现代社会使用的大多数结构材料的加工和使用过程中的基本特性，因此，理解和控制它们是必不可少的。在材料加工过程中，骨料中晶体颗粒的取向是自然发展的，其中某些理想取向变得比其他更常见。通常，这些理想方向被不同水平的方向噪声包围，这些噪声是尚未得到很好研究的微弱的次要或随机分量。用于运输、包装和能源部门的结构材料的主要供应商通常生产具有量身定制的理想取向的材料，这些材料通过其专利加工周期获得，以开发所需的材料性能。目前，多尺度模型可以预测加工过程中的平均取向发展，但无法捕捉到加工过程中形成的“微结构”晶体物质中观察到的统计偏差。这些差异可以归因于对变形原子化过程的理解的局限性，对合金元素等点缺陷对集体变形行为的作用，以及内部界面或晶界对相邻晶体之间滑移活动的交流的影响。本工作的目标是：(I)探索制备理想取向多晶材料的新方法，从而研究(Ii)样品尺寸和时间尺度对热激活变形过程的影响，(Iii)变形或加热下取向与组织稳定性之间的关系，以及(Iv)不同铝合金系统中溶质原子杂质对纳米空洞稳定性的作用及其对一般塑性的影响。这些研究确定了不同材料中的关键长度尺度特征，现有和未来的加拿大金属供应商和制造商可能会利用这些特征在新的功能材料中利用集体宏观现象，如超强或表面粗糙。

This work explores how the microstructure in oriented crystalline materials mediates the atomistic physics of slip to the larger macroscopic responses of strength and ductility. Strength and ductility are essential properties in the processing and service of most structural materials used by modern society, and so they are essential to understand and control. The orientations of crystalline grains in aggregates develop naturally during materials processing, with certain ideal orientations becoming more common than others. Often these ideal orientations are surrounded by different levels of orientation noise, which are weak minor or random components that have not been well studied. The primary suppliers of structural materials for transportation, packaging, and energy sectors usually produce materials with tailored ideal orientations obtained through their patented processing cycles to exploit desirable materials properties. Currently, multi-scale models can predict average orientation development during processing, but are unable to capture the statistical deviations observed in the crystalline matter developed as "microstructure" during processing. These variations can be attributed to limitations in understanding of the atomistic processes of deformation, the role of point defects such as alloying elements on collective deformation behaviour, and the effect of internal interfaces, or grain boundaries on communicating the slip activities between neighbouring crystals. As a way forward, the objective of this work is to (i) explore novel methods to fabricate ideally oriented polycrystalline materials so to investigate (ii) the effect of specimen size and time scales on the thermally activated process of deformation, (iii) the connection between orientation and microstructure stability under deformation or heating, and (iv) the role of solute atom impurities on the stability of nano-voids in different aluminum alloy systems and their effect on general plasticity. These studies identify key length scale features in different materials from which collective macroscopic phenomena such as ultra-strength or surface roughening might be exploited in new functional materials by existing and future Canadian metals suppliers and fabricators.