A dislocation-based model for variant selection during the γ-to-α′ transformation

A phase transformation model is described for variant selection during the austenite-to-martensite transformation. The model depends entirely on the presence of glide dislocations in the deformed austenite. The direct correlation between the 24 slip systems of the Bishop and Hill (B-H) crystal plasticity model and the 24 〈112〉 rotation axes of the Kurdjumov-Sachs (K-S) orientation relationship is employed. Two selection criteria, based on slip activity and permissible dislocation reactions, govern the variants that are chosen to represent the final transformation texture. The development of the model via analysis of the experimental results of Liu and Bunge is described. The model is applied to the four distinct strain paths: (1) plane strain rolling, (2) axisymmetric extension, (3) axisymmetric compression, and (4) simple shear. Experimental deformation and transformation textures were produced for comparison purposes via appropriate deformation and quenching procedures. In each case, the transformation texture predicted using the dislocation reaction model is in excellent agreement with the experimental findings.