Double shear mechanism and orientation relationships in austenite/ferrite steels

We propose a new approach of structural transformation between lattices by means of simple bounded transformations composed of two ''fractional shears''. The strength point of this double shear mechanism in lattice transformations is to specify particular orientation relationships. Though the basis of the model concerns the general 3D diffusionless transformation, the case of 2D lattices is presented in detail. When applied to the transformation of fcc (111) plane into the bcc (110) plane, the model is able to predict precise orientation relationships close to those observed in metallurgy (Kurdjumov-Sachs or Nishiyama-Wasserman relationships). This 2D model seems to be particularly relevant for materials such as the duplex steels. (orig.)