info:eu-repo/semantics/article
Microstructure and magnetic properties of as-cast Ni2MnGa alloys processed by twin roller melt spinning
Fecha
2013-02Registro en:
Pozo Lopez, Gabriela del Valle; Condo, Adriana Maria; Giordano, Rafael Nicolás; Urreta, Silvia Elena; Haberkorn, Nestor Fabian; et al.; Microstructure and magnetic properties of as-cast Ni2MnGa alloys processed by twin roller melt spinning
; Elsevier Science; Journal of Magnetism and Magnetic Materials; 335; 2-2013; 75-85
0304-8853
CONICET Digital
CONICET
Autor
Pozo Lopez, Gabriela del Valle
Condo, Adriana Maria
Giordano, Rafael Nicolás
Urreta, Silvia Elena
Haberkorn, Nestor Fabian
Winkler, Elin Lilian
Fabietti, Luis Maria Rodolfo
Resumen
The magnetism and the microstructure of Ni2MnGa alloys, processed by the first time by twin roller melt spinning at tangential wheel speeds of 10 m/s (V10), 15 m/s (V15) and 20 m/s (V20) are investigated. At room temperature, the major phase in the as-cast alloys is the cubic L21 Ni2MnGa ordered austenitic phase, with a lattice parameter only ~0.1% larger than the tabulated value. The order domain size in the austenitic phase decreases from (40±1) nm in samples V10 to (19±1) nm in V20. Mn(S,Se) small precipitates are also found uniformly embedded in the ribbons with mean size of (26±2) nm (V10) and (7±2) nm (V20), exhibiting a definite orientation relation with the austenitic matrix, <100>P // <100>a. The as-cast alloys transform to an intermediate cubic phase I at about 220K-230K depending on the quenching rate and to a martensitic phase at about 130K. The high temperature austenitic phase and the low temperature martensitic phase are ferromagnetic; in both cases the saturation polarization is lower in samples quenched at higher rates. The demagnetization curves measured from saturation in the martensitic state show two marked steps: a first one for positive fields in V15 and V10 (~46 mT) and a larger second one for relatively large inverse fields (~130-250 mT) in all the samples. These steps are likely to arise from a demagnetization mechanism involving a field induced twin boundary motion in the few martensite variants selected by the crystallographic texture and the quenched stresses in the ribbons.