Artículos de revistas
Curie temperature and Hopkinson effect in twin roller melt spun Ni2MnGa shape memory alloys
Fecha
2013-07-23Registro en:
Pozo Lopez, Gabriela del Valle; Fabietti, Luis Maria Rodolfo; Condo, Adriana Maria; Winkler, Elin Lilian; Giordano, Rafael Nicolás; et al.; Curie temperature and Hopkinson effect in twin roller melt spun Ni2MnGa shape memory alloys; Institute Of Electrical And Electronics Engineers; Ieee Transactions On Magnetics; 49; 8; 23-7-2013; 4514-4517
0018-9464
CONICET Digital
CONICET
Autor
Pozo Lopez, Gabriela del Valle
Fabietti, Luis Maria Rodolfo
Condo, Adriana Maria
Winkler, Elin Lilian
Giordano, Rafael Nicolás
Haberkorn, Nestor Fabian
Urreta, Silvia Elena
Resumen
The temperature dependence of the magnetic polarization near the Curie temperature in Ni MnGa stoichiometric alloys, directly processed from the melt in a twin-roller melt-spinning device, is investigated. The effect of the solidification rate on the Hopkinson peak detected is evaluated in samples quenched at three different tangential wheel speeds of 10, 15, and 20 m/s. The resulting microstructures were previously characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and by transmission electronmicroscopy (TEM). EDS results indicated that all the alloys have the composition Ni MnGa; at room temperature and above this temperature, a cubic L ferromagnetic ordered austenitic phase is observed. The Curie temperatures and the magnitude of the Hopkinson effect are estimated from the magnetic polarization versus temperature curves measured in a Faraday balance, in the range 300 K-400 K. As expected for samples with identical composition, the Curie temperatures remain insensitive to the processing route. At low fields (10 mT), the magnitude of the Hopkinson effect is larger in samples quenched at lower rates and it practically vanishes in all the alloys for applied fields near 100 mT.