GROWTH-MECHANISM OF AUCU-II PLATES

The relationship between the growth mechanisms of AuCu II and martensite plates is considered and it is concluded that lengthening and thickening of AuCu II plates involves the gliding of transformation dislocations at a rate determined by the rate of ordering at the dislocations. This mechanism, which is compatible with the phenomenological theory of martensitic transformations, is shown to account for the reported lengthening kinetics and the observed dependence of thickening rate on interface orientation. It is also shown to be capable of generating the essential features of the morphology of the pyramidal groups of four plates characteristically produced by this transformation. This morphology is not compatible with a proposed ledge mechanism in which disordered ledges are considered to migrate a thousand times faster than the plates lengthen. © 1979.