Non-isothermal transformation-mismatch plasticity: Modeling and experiments on Ti-6Al-4V

Transformation-mismatch plasticity (or transformation superplasticity) is a deformation mechanism occurring in materials undergoing a thermally-induced solid-state phase transformation, while subjected to an external stress. The classic model of this phenomenon, due to Greenwood and Johnson (Proc. Roy. Sec. Lend., 283A, pp. 403-422, 1965), is limited to the description of strain increments developed after isothermal transformations, as for pure, allotropic metals. In the present work we generalize this model to the case of a non-isothermal transformation, which is applicable to polymorphic alloys displaying a broad range of transformation temperatures. Experiments conducted on Ti-6Al-4V are used to validate the new generalized model, which predicts the strain developed after each thermal cycle, the contributions of the transformations on heating and cooling, and the kinetics of strain evolution during an individual cycle. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.