Abstract
We present in this work a simple phenomenological model of the hysteresis loop in thermoelastic martensitic transformations. The model is based on the equilibrium condition arising from the minimization of the Gibbs free energy at every transformation step. For simplicity, the simplest form of the different terms of the balance equation has been taken. From this choice some considerations are made on the contributions to the non-chemical energy that should be taken into account. Application of the model allows one to identify the role and physical meaning of the different energy contributions to the transformation behaviour, but also to predict the subloop behaviour in the validity domain of the model. The main results obtained from the model are: (i) the equilibrium condition applied to the reversible Gibbs free energies at any transformed fraction leads to the reversible path of the transformation which would be followed in absence of any irreversible contribution; (ii) the slope of the forward/reverse transformation paths is not only due to the stored elastic strain energy, but to an increasing dissipative energy as well; (iii) the knowledge of the dependence of the starting temperatures of the forward and reverse transformations on the minimum and maximum transformed fractions in a subloop is essential in order to characterize completely the global hysteresis loop and the subloop behaviour. The model is supported by experimental examples both in global and partial hysteresis cycles.
