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-induce d solid-state phase transformation, while subjected to an external stress. The classic model of this phenomenon, due to Greenwood and Johnson (Proc. R oy. 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 all oys displaying a broad range of transformation temperatures. Experiments co nducted on Ti-6Al-4V are used to validate the new generalized model, which predicts the strain developed after each thermal cycle, the contributions o f the transformations on heating and cooling, and the kinetics of strain ev olution during an individual cycle. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.