Lattice Distortion in Nano-structured Composites (2005 Science Highlight)

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Lattice Distortion in Nano-structured Composites
Copper (Cu), Niobium (Nb) and Silver (Ag) metals
all have cubic crystallographic structure. The
deformation of Cu-Ag or Cu-Nb composites produces
nanostructure, i.e. very fine structure between
the pure-Cu and pure-Nb regions of the composite
(below). These nano-composites have enormous
strength strength that greatly exceeds that of
both copper and niobium. A collaboration at the
National High Magnetic Field Laboratory measures
another result of the co-deformation the
development of short periodicity internal strains
(right), such that both of the component metals
are distorted from cubic crystallographic
structure. The lattice distortions are
anisotropic, i.e. different in different
orientations. Cyclically stretching or thermally
annealing the composite is very effective in
removing the lattice distortions, from which it
is clear that nano-scale two-phase structure is
the primary reason for the strengthening observed
in nano-composites
Lattice distortion resulting from deformation of
a nano-composite. The different strains in the
copper and niobium influence both mechanical and
transport properties of the nano-composite.
K. Han, A.C. Lawson, J.T. Wood, J.D. Embury, R.B.
von Dreele and J.W. Richardson, Jr.,
Philosophical Magazine A84, 2579 (2004)