Twin-slip and twin-twin interactions in Mo-35 at. % Re alloy

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Abstract
The crystallographic features of a twin-slip and of intersecting twins having like and unlike shear vectors have been studied in detail using transmission electron microscopy. The observations suggest that a slip dislocation on penetrating a twin dissociates into a glide dislocation in the twin and a complementary twinning dislocation; these results are consistent with the suggestion of Sleeswyk and Verbraak (1961).The intersection of twins having the same shear vector causes the cessation of widening of the crossed twin on the side which makes an obtuse angle with the boundary of the crossing twin. This observation has been rationalized in terms of the geometrical incompatibility of the atom movements necessary for simultaneous widening of both twins. The crystallographic features observed, viz. slip across certain planes in the matrix and the crossed twin, after the intersection of twins of different shear vectors, could have been caused by the penetration of the crossed twin by the glide dislocations which may result from the dissociation of twinning partials comprising the non-coherent boundary of the crossing twin.Based on these results it is suggested that in this alloy the crossed twins are unlikely to be very effective obstacles either to the slip dislocations or to the crossing twins.