Browsing by Author "Maeder, Xavier"
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Item Open Access Abnormal grain growth in ultrafine grained Ni under high-cycle loading(Elsevier, 2021-11-02) Barrios, Alejandro; Zhang, Yin; Maeder, Xavier; Castelluccio, Gustavo M.; Pierron, Olivier; Zhu, TingAbnormal grain growth can occur in polycrystalline materials with only a fraction of grains growing drastically to consume other grains. Here we report abnormal grain growth in ultrafine grained metal in a rarely explored high-cycle loading regime at ambient temperature. Abnormal grain growth is observed in electroplated Ni microbeams with average initial grain sizes less than 640 nm under a large number of loading cycles (up to 109) with low strain amplitudes (< 0.3%). Such abnormal grain growth occurs predominantly in the family of grains whose <100> orientation is along the tensile/compressive loading direction. Micromechanics analysis suggests that the elastic anisotropy of grains dictates the thermodynamic driving force of abnormal grain growth, such that the lowest strain energy density of the <100> oriented grain family dominates grain growth. This work unveils a unique type of abnormal grain growth that may be harnessed to tailor grain microstructures in materials.Item Open Access A computational and experimental comparison on the nucleation of fatigue cracks in statistical volume elements(Elsevier, 2020-04-05) Kakandar, Ebiakpo; Barrios, Alejandro; Michler, Johann; Maeder, Xavier; Pierron, Olivier N.; Castelluccio, Gustavo M.The failure of micron-scale metallic components presents significant variability as a result of their size being comparable to microstructural length scales. Indeed, these components do not represent the bulk of the material but correspond to statistical volume elements (SVEs). This work investigates the role of SVEs on fatigue crack nucleation with a novel comparison between microbeam experiments and microstructure-sensitive simulations. We recreate multiple microstructural computational realizations to estimate fatigue crack nucleation lives and orientations by means of physics-based crystal plasticity models. We demonstrate a unique approach to validate microstructure sensitive models and quantify the fatigue crack stochasticity associated with small volumes.