Simulations On The Microstructure Of The Ferromagnetic Shape Memory Alloys Ni-Mn-Ga

Ferromagnetic shape memory alloys ( FSMAs) are a new type of functional material with large magnetic-field-induced strain and high frequency. Among them the most representative one, Ni₂MnGa ferromagnetic shape memory alloy, because of its characteristics of high ferromagnetism, large magnetostriction, thermoelastic and magnetic shape memory effect, high response frequency and large strain-stress output, has attractived the considerable interests from material and physical scientists, and may become a preferred material in new magnetically-driven effect application.The magnetic-field-induced strain in ferromagnetic shape memory alloys arises not from the effect of the austenite-martensite transformation drived by magnetic field, but rather from the field-induced twin boundaries motion in the martensite state. This phenomenon is radically induced by the change of microstnicture. The characteristic and evolvement of the microstnicture of Ni₂MnGa alloy without external loading and magnetic field has been studied. First in this article, the microstnicture of Ni₂MnGa alloy without any external loading is simulated with existed geometrically nonlinear theory method. Then the evolvement of the microstnicture is simulated with introduced anisotropy energy. The simulation results accord with experiment results.In a word, our work laid the foundations for further understanding and analyzing of the microstnicture mechanism and characteristic in ferromagnetic shape memory alloys Ni₂MnGa.