Some problems in the understanding of similarities and differences between ledge-wise martensitic and ledge-wise diffusional growth were examined. It was recalled that martensitic growth could be described in terms of a lattice correspondence and a plane undistorted by the shear transformation. Diffusional growth could be similarly described in some cases, but not in others. On the basis of the Sutton–Balluffi definitions of glissile and sessile boundaries, only misfit dislocations (on terraces or risers) or orthogonal sets of disconnections provided a true sessile interface. When closely-spaced structural ledges (structural disconnections) were present during diffusional growth, they had to be glissile during the formation of a local equilibrium structure during the initial stages of growth. When they were in local equilibrium, and evenly spaced, they could move only synchronously because of their local strain interactions. Extrinsic sources of growth ledges were then required in order to move such interfaces in a diffusional manner. During martensitic growth, disconnections in the form of transformation dislocations could move freely in a synchronous manner. In this case, the apparent (undistorted) habit plane was generally useful for deducing the transformation mechanism during martensite formation. It was only occasionally so for diffusional growth. There, only the terrace plane was generally useful.

Comparison of Interfacial Structure-Related Mechanisms in Diffusional and Martensitic Transformations. H.I.Aaronson, B.C.Muddle, J.F.Nie, J.P.Hirth: Metallurgical and Materials Transactions A, 2002, 33[8], 2541-7