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Probing Deformation Mechanisms in Ultrafine Grained Al and Au Thin Films by Quantitative In Situ TEM Deformation

Understanding dislocation generation mechanisms and interactions with obstacles such as grain boundaries and other dislocations is central to understanding the mechanical behavior of metals and alloys. This has motivated decades of research into the unit processes governing dislocation interactions by in situ transmission electron microscopy (TEM) mechanical testing, resulting in the establishment of basic rules that govern how these interactions occur [1]. However, much of this research has focused on the deformation of coarse-grained polycrystals where the grain boundaries are largely isolated from each other and dislocation glide is primarily transgranular. In ultrafine grained materials, the high volume fraction of grain boundaries can lead to the activation of additional deformation mechanisms, such as grain growth, grain boundary sliding, and intergranular dislocation propagation. This paper presents results on quantitative in situ TEM experiments of deformation of ultrafine grained materials with a focus on deformation-induced grain growth. A unique aspect of this study is the ability to measure the apparent and true activation volumes associated with the material deformation using a micro-electromechanical system (MEMS)-based deformation platform.