A NEW VIEW ON MARTENSITIC TRANSFORMATIONS

The authors propose that the salient features of a static displacive premartensitic state, primarily its continuous evolution with the parent phase can be interpreted by an augmented Landau-Ginsburg model in which a new (i. e. , structural modulation) order parameter needs to specified. In terms of this model, martensite is not classically nucleated, but is finally formed by heterogeneously triggered growth of incipient variants already existing in the parent phase. They also suggest that all martensite nucleation may initiate in this manner and that in certain systems where volume changes are large (e. g. carbon steels), variations in behavior occur later in the growth stage where excessive transformation strains give rise to irreversible characteristics.