  A phase field model is presented to investigate dislocation formation
(coherency loss) and workhardening in two-phase binary alloys. In our model the
elastic energy density is a periodic function of the shear and tetragonal
strains, which allows multiple formation of slips (dislocation dipoles). By
numerically integrating the dynamic equations in two dimensions, we find that
dislocations appear in pairs in the interface region and grow into slips. One
end of each slip glides preferentially into the softer region, while the other
end remains trapped at the interface. Under uniaxial stretching at deep
quenching, slips appear in the softer regions and do not penetrate into the
harder domains, giving rise to an increase of the stress with increasing
applied strain in plastic flow.
