A modified constitutive model with an enhanced phase diagram for ferromagnetic shape memory alloys

Ferromagnetic shape memory alloys are a class of shape memory alloys which can produce inelastic strains when exposed to magnetic fields. The existing constitutive models for these alloys are mostly accompanied by a phase diagram using which critical stresses and magnetic fields for start and finish of forward and reverse reorientations are determined. In this article, an available model is modified in a continuum framework, and explicit kinetic laws together with the corresponding phase diagram in stress-field space are obtained. The proposed phase diagram is unique for a specified ferromagnetic shape memory alloy although the original model predicts different phase diagrams for different conditions. The model is further improved through a phenomenological approach to be able to capture the reported experimental findings. Numerical predictions for several stress-strain responses at different constant applied magnetic fields are compared with available experimental results. Good agreements are seen between the theoretical and empirical findings, indicating validity of the proposed model and the corresponding phase diagram in studying the magneto-mechanical behaviors of ferromagnetic shape memory alloys.