Thermodynamic Driving Forces for Martensitic Phase Transformations in Shape-Memory Alloys

Abstract

ABSTRACTA macroscopic constitutive model for the martensitic phase transformations in single-crystal shape-memory alloys (SMAs) is developed in the framework of irreversible thermodynamics with internal variables. Central to the model is the notion that the rate of progression of structural rearrangements on the microscale depends on the stress state through the thermodynamic forces conjugate to the rearrangements. These thermodynamic forces, i.e. the driving forces for the phase transitions, are shown to have an important contribution that arises from changes in the effective elastic response of the SMA, which in turn depend upon the state of transformation. This contribution is shown to have a significant effect on the overall macroscopic stress-strain response.