Nano-twinned materials are the subject of many researches because they show mechanical properties that are usually antagonistic, namely high yield strength and good ductility [1]. We performed tensile tests on gold thin films with nanotwins (figure 1.a), in-situ under X-ray diffraction and we observed, for some loading axes, the growth of twins in the crystal [2]. We have performed atomistic simulations with commonly used interatomic potentials for gold as a complementary tool to better understand the deformation mechanisms occurring in these materials (figure 1.b). We have studied interactions between coherent twin boundaries (CTBs) and between incoherent twin boundaries (ITBs, figure 1.c) for two extreme cases (with close surfaces and without any surfaces, to simulate a relaxed or constrained system). The estimated displacement fields give the extension of interactions between twin boundaries which are 6 and 48 atomic planes respectively for the CTB and for the ITB. The residual stress introduced by the twin boundaries in the constrained system and the associated elastic energy are deduced from the excess volumes, which have been determined in a previous work [3]. Afterward, we have studied the behavior of a thin film with finite nano-twins under different temperatures. We have discussed the faceting and the migration of the incoherent twin boundaries observed in the thin film. We now aim at deforming the system in order to confront the simulation results to the experimental observations.    


References
[1] L. Lu et al. Science, 2009, 323, 5914.
[2] J. Drieu La Rochelle et al. Surf. Coat. Technol.,2019, 377, 124878.
[3] Y. F. Woguem et al. Mater., 2023, 27, 101678.