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A
partial dislocation has a Burgers vector that is shorter than a unit lattice
translation vector for the crystal structure. The slip associated with
the creation of the dislocation must displace atoms from one stable site
to another. If this displacement is not a unit vector of the lattice, the
creation of the dislocation will also cause a local stacking error (a stacking
fault) on the slip plane of the dislocation. This stacking fault has an
energy per unit area associated with it.
The
photograph and explanatory diagram show partial dislocations in a Cu-7
wt% Al alloy. The substitutional alloy has an fcc crystal structure. In
this lattice the dissociation of the unit dislocation: b = (a/2)< 1
1 1 > into two Shockley partial dislocations with bS
= (a/6) < 2 1 1> is favored, and a region of stacking fault occurs between
the two partial dislocations.
From:
Hull, "Introduction to Dislocations," Pergamon (1965) |
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