Abstract
Fine structures of deformation twins in 3% Si-Fe alloy have been investigated by transmission electron microscopy and selected-area electron diffraction. Inside the twins, dislocations were seen to be fairly straight and almost parallel to one direction in contrast to those in the matrix. The twin boundary was usually crowded by dislocations. It was most interesting that a mid-rib was occasionally found in the twin in the same way as in the martensite crystal. This mid-rib was found to be an extremely thin plate parallel to {112} twinning planes and to be composed of tangled dislocations and dislocation loops of high density. In some cases the mid-rib was observed as a small angle boundary. Dislocation pile-ups in the twin were found on its {110} slip planes. On the twin boundary indentations were frequently found to have a cross section of the equilateral triangular shape, two edges of which were always parallel to the slip planes.
All of the above phenomena are considered to be associated with the formation mechanism of the deformation twin.
