Model calculation of 3D-phase transformation diagram of ferromagnetic shape memory alloys

A stress–magnetic field–temperature phase diagram of polycrystalline Fe–30.5%Pd ferromagnetic shape memory alloy (FSMA) is constructed based on experimental results and a thermodynamic model. The 3D-phase transformation diagram provides a key performance map in guiding us which actuation mechanism is the best for a given FSMA. According to this 3D-phase transformation diagram, the magnetic field induced transformation is found to be insignificant, while the hybrid mechanism based on the stress-induced martensitic transformation induced by the magnetic field gradient is more attractive. The NiMnGa system is also examined.