Deformation Response of Oriented Crystalline Aggregates: Experiment and Theory

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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.