Dynamics and atomic structure of martensite-austenite interfaces

The structure of the lowest energy interface between an hcp austenite phase and an fcc martensite phase of similar atomic volumes has been simulated by annealing a disordered region between the two perfect lattices until semi-coherent intergrowth occurred. The two structures wee oriented so that the closepacked planes were parallel, and closepacked directions were aligned. The dynamics of this interface and the structure which it evolved as it moved was then studied by applying a transformation driving force through the use of an Embedded Atom Method potential. Initially the interface moved in a reconstructive, diffusive manner but eventually it developed a highly mobile, diffusionless form which moved at about one third of the shear sound velocity. The structure of this rapidly moving interface could be analyzed in terms of three different types of Shockley partials arranged in sequence, but passing at slightly different times. This paper reports that this structure agrees with some elements of a model previously proposed by Christian to describe the transformation in pure Co, and agrees with other elements of a proposal of McGreer, Lundgren and Franck to explain their observations of the transformation in 4He. Neither fully explain our observations