Article Dans Une Revue Acta Materialia Année : 2023

Revealing 3D intragranular micromechanical fields at triple junctions

Résumé

In polycrystalline solids, triple junctions (intersections of three or more grains) are regions with complex morphological compatibility requirements and are known to be locations of stress concentrations and strain localization. In this work, the intragranular lattice curvatures and elastic strains at triple junctions are investigated via a novel zoom-in style combination of synchrotron X-ray techniques. It is found that the highest values of intragranular misorientation metrics lie closer to triple junctions compared to grain boundaries (between two grains), and that the triple junctions exhibited higher values of these metrics. A heterogenous distribution of intragranular misorientations, elastic strains, and dislocation density was observed along a single triple junction line, with the two triple junction line end points (quad points) exhibiting different micromechanical fields. Finally, the calculation of the dislocation density via the Nye dislocation tensor is revisited. Specifically, the impact of considering elastic strain gradients to be negligible when constructing the Nye tensor is evaluated in a lightly-deformed grain. Similar magnitudes of lattice curvature and elastic strain gradients are found for a component of the Nye tensor. By not including the contribution of the elastic strain gradient, the dislocation density was underestimated at a hotspot region by 27% of the maximum dislocation density value in the entire reconstruction. This work provides a unique 3D view of triple junctions and highlights their spatially heterogenous micromechanical response, while also indicating the importance of including elastic strain gradients when evaluating the dislocation density.

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hal-04305077 , version 1 (24-11-2023)

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Sven E Gustafson, Wolfgang Ludwig, Raquel Rodriguez-Lamas, Can Yildirim, Katherine S Shanks, et al.. Revealing 3D intragranular micromechanical fields at triple junctions. Acta Materialia, 2023, 260, pp.119300. ⟨10.1016/j.actamat.2023.119300⟩. ⟨hal-04305077⟩
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