Properties of NiMnGa Alloys Ultra Rapidly Solidified by Suction Casting

Rodoni, Esteban; Levingston, Jorge M.; SebastiánDeghi,; Lescano, D.; López, Graciela; Urreta, S.E.; Fabietti, L.M.

doi:10.1016/j.mspro.2015.04.111

Cited by 1 publication

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“…Another maximum is observed at about -0.3 T. This behavior is completely reproducible during subsequent field cycles. The largest step has already been found in Ni-Mn-Ga polycrystalline melt spun ribbons [16,20,21], and in massive cylindrical samples [42]. It has been attributed to magnetic induced reorientation (MIR) of variants in the martensitic phase, as previously proposed by other authors [43][44][45].…”

Section: Magnetic Propertiesmentioning

confidence: 54%

Microstructure and magnetic properties of as-cast Ni2MnGa rods and tubes solidified by suction casting

López

Condó

Limandri

et al. 2019

Materials Characterization

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Ni 2 MnGa cylinders and tubes are solidified in water chilled copper molds, a few millimeters in external diameter and five centimeters long, by the suction casting technique. At room temperature, all samples are in cubic austenitic phase. Microstructure and crystallographic texture of the as-cast rods and tubes are characterized by XRD, SEM, EBSD and TEM. Because of the heat extraction geometry samples exhibit a strong texture, with the [100] direction preferentially oriented in the radial direction, together with a random distribution on the long axis. This texture is more marked in the tubes. XRD and TEM results indicate that the major austenitic phase is fcc, with L2 1 order. A minority volume of the equilibrium B2´ disordered phase is detected by the presence of two close Curie temperatures in cylinders and tubes 2 mm in external diameter, but not when this diameter is near 1 mm. Precipitates of the stable compounds α-Mn(S,Se), with a NaCl-type structure, and monoclinic P 4 S 5 are observed in all the samples. Cylinders and tubes in austenitic phase are magnetically soft. Hysteresis loops in martensitic phase exhibit local steps associated to a magnetization mechanism involving twin boundary displacement, indicating that a field-induced variant reordering takes place. The switching field H sw , corresponding to the magnetization step observed, is identified as the field at which twin boundaries become mobile. The measured values of 0.

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