title: Slip-activated surface creep with room-temperature super-elongation in metallic nanocrystals.
abstract: Nanoscale metallic crystals have been shown to follow a 'smaller is stronger' trend. However, they usually suffer from low ductility due to premature plastic instability by source-limited crystal slip. Here, by performing in situ atomic-scale transmission electron microscopy, we report unusual room-temperature super-elongation without softening in face-centred-cubic silver nanocrystals, where crystal slip serves as a stimulus to surface diffusional creep. This interplay mechanism is shown experimentally and theoretically to govern the plastic deformation of nanocrystals over a material-dependent sample diameter range between the lower and upper limits for nanocrystal stability by surface diffusional creep and dislocation plasticity, respectively, which extends far beyond the maximum size for pure diffusion-mediated deformation (for example, Coble-type creep). This work provides insight into the atomic-scale coupled diffusive-displacive deformation mechanisms, maximizing ductility and strength simultaneously in nanoscale materials.
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Zhong
authors.affiliation: Department of Mechanical Engineering and Materials Science Program, The University of Vermont, Burlington, Vermont 05405, USA.
authors.forename: Frederic
authors.identifier: 0000-0002-2782-1832
authors.initials: F
authors.lastname: Sansoz
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: He
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Chongmin
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Scott X
authors.initials: SX
authors.lastname: Mao