title: Grain rotation mediated by grain boundary dislocations in nanocrystalline platinum.
abstract: Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials. In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm. Here, in tensile-loaded Pt thin films under a high-resolution transmission electron microscope, we show that the plasticity mechanism transitions from cross-grain dislocation glide in larger grains (d>6 nm) to a mode of coordinated rotation of multiple grains for grains with d<6 nm. The mechanism underlying the grain rotation is dislocation climb at the grain boundary, rather than grain boundary sliding or diffusional creep. Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank-Bilby dislocation content in the grain boundary.
authors.affiliation: 1] Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China [2].
authors.forename: Lihua
authors.initials: L
authors.lastname: Wang
authors.affiliation: 1] Department of Material Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083, China [2].
authors.forename: Jiao
authors.initials: J
authors.lastname: Teng
authors.affiliation: 1] WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan [2].
authors.forename: Pan
authors.initials: P
authors.lastname: Liu
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hirata
authors.affiliation: Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: En
authors.initials: E
authors.lastname: Ma
authors.affiliation: 1] Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China [2] State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310008, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Mingwei
authors.initials: M
authors.lastname: Chen
authors.affiliation: Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Han