THE MOTION OF MULTIPLE HEIGHT LEDGES AND DISCONNECTIONS IN PHASE-TRANSFORMATIONS

For phase transformations with well-defined terrace planes, interface motion can occur by the motion of ledges or disconnections (ledges wit h added dislocation character). Symmetry imposes restrictions on the n ature of these defects and may lead to the need for multiple height le dges. The structure of the ledge riser can also be variable. These pos sibilities impose constraints that can influence the motion of the def ects and hence affect the rate of phase transformation. Examples of th ese phenomena are presented for interfaces with differing degrees of l attice matching.