Shape memory effects of Ni_49.7Mn_25.0Ga_19.8Fe_5.5 microwires prepared by rapid solidification

We report a systematic study of a new class of melt-extracted Ni_49.7Mn_25.0Ga_19.8Fe_5.5 polycrystalline microwires in terms of fabrication, microstructural characterization, and evaluation of shape memory effects (SMEs). The as-extracted microwire has enhanced ductility due to its fine grains with diameters of 1-3 μm. The total strain in its martensite state reached 2.14% as loading at 350 MPa and 100% plastic deformation strain recovery was achieved after heating process. During thermo-cycling tests, a fully recoverable transformation strain of 1.5% was obtained under a tensile bias-stress of 468 MPa. It can be therefore concluded that Fe-doped microwires display the least strain dependence on stress compared with other alloys such as Ni-Ti and NivMn-Ga, and could be useful in devices required constant stress output.