High-frequency response (about 1000 Hz) and large reversible strain of Ferromagnetic (or magnetic) Shape Memory Alloys (FSMAs) make them proper candidates for sensors and actuators. Sofar, they have been usually investigated under a simple 1D condition: An axial compressive stress together with a transverse magnetic field. To obtain field-induced variant switching, however, the compressive stress (output stress) is limited by a small blocking stress ( 10 MPa, mainly governed by the materials’ magnetic anisotropic energy). Recent experiments on biaxial compression of FSMAs show that these alloys can work at high levels of biaxial or multi-axial stresses while keeping their advantages - low intrinsic dissipation and large reversible strain. In the present work, martensite reorientation in a single crystal tetragonal five-layered modulated martensitic (5M) Ni–Mn–Ga was experimentally studied under complete and incomplete biaxial loadings. To this end, a special test rig was designed and manufactured to equip a uniaxial compression testing machine with appartus for applying a constant lateral compressive load. Also, the equipment has ability to induce a magnetic field in the third axial direction in order for 3D loading purposes. In 2D stress states, different dead loads were applied in the specimen’s lateral direction, and stress–strain responses in the axial direction were obtained at different loading conditions. Quasiplastic response was seen when no lateral stress was applied, but transition to psueduelasticity was observed by gradually increasing the constant lateral compression. Moreover, by increasing the applied lateral compressive load, higher axial stresses were shown to be required for start and finish of maretnsite reorientation. Stress–strain responses under different amounts of constant biaxial compressions were obtained for several complete and incomplete loading–unloading cycles to investigate behaviors of an FMSA when different kinds of interruptions are imposed in the course of loading or unloading. The so-called strain hardening and return point memory phenomena were observed in the alloy. Different behaviors were also seen between elastic and ineslatic interruptions. In 3D loadings, there was seen no effect while appling magnetic field or compressive stress on the sample’s third direction. Accordingly, the third axial (axial z) was introduced as a neutral direction. Keywords: Ferromagnetic Shape Memory Alloy, Ni-Mn-Ga, Martensite Reorientation, Twin Boundary Motion, Biaxial Compression, Incomplete loading, Multi-axial Loading, Strain Hardening, Return Point Memory.
