Adriana Eres-Castellanos

Building upon a previous demonstration of the viability of plasma focused ion beam irradiation to study radiation effects in pure silicon, the present work extends this methodology to metallic systems representative of structural alloys used in nuclear applications. Using pure high-purity aluminum foils, we evaluate irradiation-induced damage by studying the formation of dislocation loops as a function of average damage dose. Damage calculations are performed and the experimental results are complemented by a discussion on the particular challenges of this technique and perspectives for future work, including heterogeneous damage across the irradiation profile and high dose rates.

Crystallographic textures are a major determinant of the macroscale anisotropic properties of polycrystalline metallic alloys produced in a wide range of additive manufacturing (AM) processes. Here, we introduce a statistical method that can accurately quantify the degree of orientational order of textures despite the large random fluctuations in the orientation of individual grains inherent in AM processes. The method, demonstrated for laser and resolidification of AlSi thin films, extends Z-scoring to a dynamical regime to assess the statistical significance of observed textures compared to randomly generated ones at different stages of solidification. We further show that, combined with phase-field modeling, this method can be used to infer fundamental anisotropic properties of the solid-liquid interface that are essential for texture prediction, and are compared here to the results of atomistic simulations. In addition, phase-field modeling reveals that, even at rapid AM solidification rates, the observed 〈110〉-dominated textures in the AlSi thin films are controlled predominantly by the anisotropy of the interface free-energy and sheds light on the physical mechanism of grain competition. These results significantly enhance both the existing tools for the quantification and prediction of AM crystallographic textures and our basic understanding of their formation.

Ausforming processes are those thermomechanical treatments in which austenite is plastically deformed before either a martensitic or a bainitic transformation takes place. Although the deformation of an austenitized steel at intermediate temperatures has many benefits, it can also induce displacive transformations, sometimes unavoidably at the industrial level. Although the addition of a mechanical driving force, associated to the applied stress, has been shown to accelerate the bainitic transformations and promote transformation plasticity and variant selection, little information is found on the effect of stress on parameters such as bainitic ferrite plate thickness or volume percentage of retained austenite. Some works suggest that constant stresses can coarsen bainitic ferrite plates and increase the amount of transformed bainitic ferrite, although no systematic work has been conducted in this regard. This work aims to better understand the characteristics of bainitic microstructures formed during the application of stress or under constant stress and discuss the mechanisms affecting the bainitic transformations. Among the obtained results, it can be highlighted that, at temperatures below the bainite start temperature, bainitic ferrite plates formed during straining are more refined that isothermally formed plates at the same temperature, whereas constant stresses leads to an increased fraction of coarser bainitic ferrite plates, as compared to those microstructures obtained at the same temperature.