DOUBLE SHEAR MECHANISM AND ORIENTATION RELATIONSHIPS IN AUSTENITE FERRITE STEELS

We propose a new approach of structural transformation between lattice s by means of simple bounded transformations composed of two << fracti onal shears >>. The strength point of this double shear mechanism in l attice transformations is to specify particular orientation relationsh ips. Though the basis of the model concerns the general 3D diffusionle ss transformation, the case of 2D lattices is presented in detail. Whe n 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-Wa sserman relationships). This 2D model seems to be particularly relevan t for materials such as the duplex steels.