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Tailoring deformation-induced effects in Co powders by milling them with α–Al2O3

Published online by Cambridge University Press:  31 January 2011

E. Menéndez ,
J. Sort ,
S. Suriñach ,
M.D. Baró  and
J. Nogués
E. Menéndez
Affiliation:
Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
J. Sort*
Affiliation:
Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
S. Suriñach
Affiliation:
Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
M.D. Baró
Affiliation:
Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
J. Nogués
Affiliation:
Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

The evolution of the structural and magnetic properties of metal-ceramic, cermet, nanocomposite powders, consisting of Co and α–Al2O3 in different proportions, prepared by ball milling has been investigated. The overall microstructure of the system, after long-term milling, is found to be very sensitive to the amount of α–Al2O3, yielding a less refined and faulted hexagonal-close-packed (hcp)-Co structure for the sample with larger α–Al2O3 percentage. The increased presence of the ceramic counterpart also causes a delay of the face-centered-cubic (fcc) to hcp-Co stress-induced transformation during ball milling. The results seem to indicate an evolution of the role of α–Al2O3, from increasing locally the strain rate of the mechanical work for small amounts of ceramic to absorbing milling energy for large amounts of α–Al2O3. The magnetic properties correlate with the obtained microstructure, where the amount of hcp-Co and stacking faults and the isolation of the Co particles by the α–Al2O3 control the coercivity.

Keywords

Mechanical alloyingMicrostructureMagnetic properties
Type
Articles
Information
Journal of Materials Research , Volume 22 , Issue 11 , November 2007 , pp. 2998 - 3005
Copyright
Copyright © Materials Research Society 2007

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