Ni2MnGa shape memory alloys processed by twin roller melt spinning

G. POZO LÓPEZ; L.M. FABIETTI; A.M. CONDÓ; R. GIORDANO; S.E. URRETA; N. HABERKORN; E. WINKLER

Workshop; X-LAW3M, Latin American Workshop on Magnetism, Magnetic Materials and their Applications; 2013

Ni2MnGa stoichiometric alloys were, for the rst time, directly processed from the melt in a twin-roller melt-spinning device. Three different tangential wheel speeds (10 m/s, 15 m/s and 20 m/s) were selected to impose different quenching rates; the resulting microstructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X ray spectroscopy (EDS) and by transmission electron microscopy (TEM). The martensitic transformation temperatures for each microstructure condition were determined by electrical resistance measurements, and the corresponding Curie temperatures were estimated from magnetization vs. temperature curves measured in a Faraday balance, in the 300 K - 400 K temperature range. At room temperature, all the alloys are in the cubic L2_1 Ni2MnGa ferromagnetic ordered austenitic phase; they exhibit a preferential orientation of the [400] direction perpendicular to the ribbon plane, which becomes more marked as the quenching rate increases. Martensitic transformation temperatures are lower than those measured in bulk single crystals of Ni2MnGa alloys, while the Curie temperatures remained insensitive to the processing route.