It was shown that deformation twinning in face-centered cubic structures could be described by a double dislocation-pole model. The model configuration consisted of 2 screw pole dislocations of a/2<110>-type, with opposite Burgers vector, and a separate dislocation of similar Burgers vector that dissociated into 2 Shockley partials of opposite Burgers vector on a {111} plane which was approximately perpendicular to the poles. This type of dislocation configuration was likely to be present in deformed specimens; particularly at sub-grain boundaries and in regions close to grain boundaries. There were 2 stress barriers to the nucleation of a twin. One was the passing stress, and the other was the Orowan stress. The former was a short-range barrier, and could therefore be surmounted via thermal activation. The other barrier was a long-range one which required a sufficiently high applied stress. As a result, there existed a minimum value of the spacing of 2 pole dislocations at a given stress. The resultant predictions of thermal sensitivity, nucleation and growth kinetics of the twinning process, and of the contrast pattern of stacking faults that were associated with twin tips, were in good agreement with experimental observations of twinning in face-centered cubic metals.

Dislocation Pole Model for Deformation Twinning in Face-Centered Cubic Lattices. S.G.Song, G.T.Gray: Philosophical Magazine A, 1995, 71[3], 661-70