Strain mapping of a triple junction in nanocrystalline Pd
H Rosner and C Kubel and Y Ivanisenko and L Kurmanaeva and SV Divinski and M Peterlechner and G Wilde, ACTA MATERIALIA, 59, 7380-7387 (2011).
Aberration-corrected transmission electron microscopy was used to provide structural information on a triple junction in nanocrystalline Pd. This triple junction consists of two intersecting Sigma 3 twin boundaries with a Sigma 9 grain boundary and is connected to a quadruple point via the Sigma 9 grain boundary. A comprehensive strain analysis of this triple junction using geometric phase analysis is presented and compared with a molecular dynamics simulation. The main results are: (i) the strain field of the core of the triple junction shows dislocation character and extends over a distance of about 0.5 nm; (ii) the intersecting boundaries result in a net translation of a(0)/root 2 which corresponds to a Burgers vector of an a(0)/2 < 1 1 0 > dislocation in the fcc lattice; (iii) a disclination emerging from the triple junction along the Sigma 9 grain boundary is balanced by a disclination of opposite sign emerging from the quadruple point. Based on the observation that the core of the triple junction can be described by the strain field of a dislocation, its energy was estimated using 1/2Gb(2) to be about 1.7 x 10(-9) J m(-1). The presence of a disclination dipole is thought to be essential for stabilization of the structure observed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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