A dislocation-based model for variant selection during the gamma-to-alpha ' transformation

A phase transformation model is described for variant selection during the austenite-to-martensite transformation. The model depends entirely on the p resence of glide dislocations in the deformed austenite. The direct correla tion between the 24 slip systems of the Bishop and Hill (B-H) crystal plast icity model and the 24 [112] rotation axes of the Kurdjumov-Sachs (K-S) ori entation relationship is employed. Two selection criteria, based on slip ac tivity and permissible dislocation reactions, govern the variants that are chosen to represent the final transformation texture. The development of th e model via analysis of the experimental results of Liu and Bunge is descri bed. The model is applied to the four distinct strain paths: (1) plane stra in 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 di slocation reaction model is in excellent agreement with the experimental fi ndings.