Speaker
Description
The modification in the dimensions of a material leads to changes in its properties, especially the mechanical properties. In recent years, it has been shown that nanotwinned metals have two mechanical properties that are usually antagonistic, namely high yield strength and good ductility [1]. We performed tensile tests on gold thin films with nanotwins, in-situ under X-ray diffraction [2]. Atomistic simulations are a useful complementary tool to better understand the deformation mechanisms occurring in these films. As a first step, molecular statics calculations are used to characterize the interactions between twin boundaries in these thin films. We first focused on the ∑3{111} coherent twin boundaries (CTB) which can be defined as the mirror plane separating the parent crystal and the twin. Using different system geometries, we determine the CTB energy and the expansion of the atomic planes of the lattice produced by the introduction of the CTB in the crystal. We then consider the interactions between CTBs and we propose a simple mathematical model for the interaction energy. The introduction of ∑3{121} incoherent twin boundaries allows us to study the finite twins we observe experimentally. We now aim at characterizing how the geometry of the twins governs the mechanical properties of the thin films.
[1] D. Jang et al. « Deformation mechanisms in nanotwinned metal nanopillars ». Nat. Nanotechnol. 7(9), 594 (2012), doi: 10.1038/nnano.2012.116.
[2] J. Drieu La Rochelle et al. « Study of uniaxial deformation behavior of 50 nm-thick thin film of gold single crystal using in situ X-ray pole figure measurements ». Surf. Coat. Technol. 377, 124878 (2019), doi: 10.1016/j.surfcoat.2019.06.103.
| Speaker Country | France |
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