Model Calculation of Stress-Strain Relationship of Polycrystalline Fe- Pd and 3D Phase Transformation Diagram of Ferromagnetic Shape Memory Alloys

A micromechanics approach is proposed to calculate the stress-strain relationship of a polycrystalline Fe-Pd ferromagnetic shape memory alloy. It is modeled as consisting of spherical grains, which are grouped according to their orientations with respect to the loading axis. Therefore, the internal stress and elastic energy are accumulated as straining proceeds due to the strain differences between differently oriented grains. In the present study, the energy dissipation of the interface movement is also considered. Furthermore, a stress-magnetic field-temperature phase transformation diagram is constructed. The magnetic field induced transformation is found to be insignificant based on thermodynamics model. The cases of Fe-Pd and NiMnGa systems are examined for 3D phase transformation diagram.