Artículo
As cast precipitation microstructures in twin-roller melt-spun Cu 90 Co 10 alloys
Núñez Coavas, Henry; Pozo Lopez, Gabriela del Valle
; Condo, Adriana Maria
; Urreta, Silvia Elena; Fabietti, Luis Maria Rodolfo
Fecha de publicación:
12/2016
Editorial:
Elsevier Science Inc
Revista:
Materials Characterization
ISSN:
1044-5803
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Resumen
As cast Cu 90 Co 10 ribbons rapidly solidified by twin-roller melt spinning, exhibit special microstructure features. This processing method provides scenarios where a different phase selection takes place; coherent Co precipitates form directly from solidification, with neither a spinodal-like composition oscillation nor a discontinuously precipitated laminar phase. Samples are processed at tangential wheel speeds of 10 m/s (V10), 15 m/s (V15), 20 m/s (V20) and 30 m/s (V30). Microstructures resulting from this single step process are characterized and the hysteresis properties and the magnetoresistance effects evaluated. Samples V30 have a quite uniform density of coherent precipitates, with a narrow size distribution around 4 nm. On contrary, non-uniform precipitate distributions are found in samples cooled at lower rates; zones with a high density of coherent Co-rich precipitates are found forming colonies. These colonies are consistent with the extended compositional fluctuations occurring during very early stages in the cooling process. Samples may exhibit wide (V10) and even bimodal (V15) size distributions. Only samples V30 behave close to the ideal superparamagnetism. Samples V20 present relatively large coercivity and relative remanence and behave as an interacting superparamagnet, while the hysteresis loops of ribbons cooled at lower rates exhibit a ferromagnetic contribution in addition to the superparamagnetic-like one. This ferromagnetic component arises from blocked precipitates, larger than the upper bound size for superparamagnetic behavior at 300 K (12 nm). Room temperature magnetoresistance values associated to granular scattering units decrease as the mean precipitate size increases, but they remain below 2%, which is lower than that measured in samples annealed after rapid solidification, indicating that in this latter case contributions from the spinodally segregated matrix take place in addition to that of Co granules.
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Articulos(CCT - PATAGONIA NORTE)
Articulos de CTRO.CIENTIFICO TECNOL.CONICET - PATAGONIA NORTE
Articulos de CTRO.CIENTIFICO TECNOL.CONICET - PATAGONIA NORTE
Articulos(IFEG)
Articulos de INST.DE FISICA ENRIQUE GAVIOLA
Articulos de INST.DE FISICA ENRIQUE GAVIOLA
Citación
Núñez Coavas, Henry; Pozo Lopez, Gabriela del Valle; Condo, Adriana Maria; Urreta, Silvia Elena; Fabietti, Luis Maria Rodolfo; As cast precipitation microstructures in twin-roller melt-spun Cu 90 Co 10 alloys; Elsevier Science Inc; Materials Characterization; 122; 12-2016; 54-62
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