|
|
||||
|
|
||||
|
The
diagrams show nanocrystalline copper clusters of about 100,000 atoms.
In a) the undeformed structure is shown, the blue atoms being in the
grain boundaries between the variously oriented nanocrystals. After
10% plastic deformation (b), partial dislocations have passed through
the crystallites leaving regions of stacking fault (red). The green
arrow shows a partial dislocation that has not yet passed through the
crystalite. Grain boundary sliding has occured and increased the fraction
of atoms in the grain boundaries. Both processes contribute to the plastic
deformation of the sample. The dominance of the grain boundaries in
the very small crystalite (3 to 7 nm) samples causes softening with
decreasing grain size - an inverse Hall-Petch effect!
From:www.fysik.dtu.dk/CAMP/hot0005.html
|
||||
