ON THE ROLE OF INTERPHASE-BOUNDARY STRUCTURE IN PLATE GROWTH BY DIFFUSIONAL MECHANISMS

The structures of planar phase interfaces and of interfacial defects r esponsible for their diffusional migration are discussed in terms of e xtensions of the 0-lattice concept, in which the intersection of the t wo structures is treated analytically. Two cases are considered and il lustrated with well-characterized experimental examples: one in which two-dimensional structural matching leads to 0-planes, and a second in which linear matching yields an array of 0-lines. It is suggested tha t growth ledges moving normal to the 0-lines will often require latera l kink formation and motion for their propagation. The misfit associat ed with transformation ledges is modeled in terms of real (screened) d islocations, which may coexist with virtual (unscreened) dislocations representing a residual component of misfit. A macroscopic shear can r esult from the cumulative action of transformation ledges with shear c omponents parallel to the habit plane.