Dislocation line stability in Ni 3 AI

The equilibrium shapes of dissociated dislocations in strained Ni3Al poly-crystals have been investigated by weak-beam electron microscopy and the results compared to the predictions derived from the theory of anisotropic elasticity. Where dislocations are dissociated exclusively by glide the agreement is good. However, it is shown that climb dissociation induces further instabilities in the shape of dislocation segments with pronounced edge characters. The results are applied to explain the repeated observation of long dislocations deviating by 25° from the exact screw character.