title: Dislocation-mediated relaxation in nanograined columnar palladium films revealed by on-chip time-resolved HRTEM testing.
abstract: The high-rate sensitivity of nanostructured metallic materials demonstrated in the recent literature is related to the predominance of thermally activated deformation mechanisms favoured by a large density of internal interfaces. Here we report time-resolved high-resolution electron transmission microscopy creep tests on thin nanograined films using on-chip nanomechanical testing. Tests are performed on palladium, which exhibited unexpectedly large creep rates at room temperature. Despite the small 30-nm grain size, relaxation is found to be mediated by dislocation mechanisms. The dislocations interact with the growth nanotwins present in the grains, leading to a loss of coherency of twin boundaries. The density of stored dislocations first increases with applied deformation, and then decreases with time to drive additional deformation while no grain boundary mechanism is observed. This fast relaxation constitutes a key issue in the development of various micro- and nanotechnologies such as palladium membranes for hydrogen applications.
authors.affiliation: Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: M-S
authors.initials: MS
authors.lastname: Colla
authors.affiliation: Department of Physics, Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Amin-Ahmadi
authors.affiliation: 1] Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium [2] Department of Physics, Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Idrissi
authors.affiliation: 4MAT: Materials Engineering, Characterization, Synthesis and Recycling, Université Libre de Bruxelles, 50 Avenue FD Roosevelt CP194/03, 1050 Brussels, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Malet
authors.affiliation: 4MAT: Materials Engineering, Characterization, Synthesis and Recycling, Université Libre de Bruxelles, 50 Avenue FD Roosevelt CP194/03, 1050 Brussels, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Godet
authors.affiliation: Information and Communications Technologies, Electronics and Applied Mathematics (ICTEAM), Université catholique de Louvain, Place du Levant 3, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: J-P
authors.initials: JP
authors.lastname: Raskin
authors.affiliation: Department of Physics, Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Schryvers
authors.affiliation: Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: T
authors.initials: T
authors.lastname: Pardoen