Role of Diffusion-Induced Grain Boundary Migration in Alloy Oxidation
Oxidation resistance remains a critical requirement for materials applications at medium to high temperatures. Decades of studies have generated significant knowledge about how to improve the oxidation resistance of structural materials, with strategies including the use of alloying elements, coatings, and surface treatments. However, many of the mechanisms behind these strategies remain elusive limiting our ability to design better performing alloys. In this context, the project will address the impact of deformation and small grain sizes on the oxidation response of selected structural alloys. The work specifically will focus on elucidating the key role of diffusion along moving grain boundaries by a mechanism known as diffusion-induced grain boundary migration or DIGM, supplying elements to the alloy surface to form an oxide layer. This ubiquitous mechanism had been largely ignored and therefore unexplored in the context of alloy oxidation; yet it could explain the beneficial or detrimental role of surface deformation and small grain sizes on the oxidation behavior of alloy systems. This thesis will investigate the role of DIGM in a series of alloys, from simpler to more complex and quantify its impact and relevance depending on alloy composition and oxidation conditions.
This these will expand on our preliminary work: Role of diffusion-induced grain boundary migration in the oxidation response of a Ni-30Cr alloy, F Xue, EA Marquis, Acta Materialia (2022) 240, 118343 doi.org/10.1016/j.actamat.2022.118343
The project will involve experimental work from alloy processing, oxidation experiments including thermogravimetry, and microstructure characterization using a range of techniques from the micron scale down to the atomic scale such as scanning electron microscopy, transmission electron microscopy, and atom probe tomography, with all techniques available at the University of Michigan.