The structure and its dependence on the magnetic properties of Ni 5CoXCu95-X alloys produced by mechanical alloying and subsequent annealing

Marta López, M. Elena Gómez, David Reyes, K. Ramam, R. V. Mangalaraja, Pedro Prieto, José Jiménez

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations

Abstract

Lower energy-ball milling was used to prepare magnetic granular Ni 5CoXCu95-X alloys produced by mechanical alloying through a milling process and subsequent annealing process, have been investigated. The pure copper shows high electrical conductivity and malleability, however the Cu-Co system in the thermodynamic equilibrium is non-soluble below 500°C. Nevertheless, mechanical alloyed particles of Cu with 5-7%Co and 5%Ni can be subjected to annealing at 500°C or consolidation-sintering treatments to obtain composite materials thereby improving their mechanical and magnetic properties suitable for electronic devices. The ultrafine Co and (Co,Ni) particles reduced and dispersed in the copper powder matrix with milling times of 20 to 60 h and thus affected the magnetic properties of the as-milled Ni5CoXCu 95-X powder obtained from this nonequilibrium phases synthesis. The magnetic properties of the supersaturated solid solutions are strongly dependent on the interactions among the magnetic particles and the nanometric size of these particles. The morphology, structure and size of as-milled and sintered powders were characterized by SEM, HRTEM and XRD techniques. The results show that the microstructure, hardness and magnetic properties of the granular Ni5CoXCu95-X alloy have strong dependence of milling time. The continuous decrement of Ms as a function of milling time is a consequence to the variation of phase in the composition with formation of CoNi particle and the partial change of fcc-Co to hcp-Co. Super-paramagnetic behavior is observed in both as-milled and annealed powders, with a maximum Hc of 250-260 Oe obtained for 7%Co after 60h of milling. The effect of Nickel on the Ni5CoXCu 95-X can be explained as Ni content inhibit the two-solid (Cu-Co) phases segregation of the alloys when annealed at high temperature, leading to a grained structure with precipitated Co particles in homogeneous Cu-Ni strengthened solid solution matrix.

Original languageEnglish
Title of host publicationTHERMEC 2009
EditorsTara Chandra, Tara Chandra, Tara Chandra, N. Wanderka, N. Wanderka, N. Wanderka, Walter Reimers, Walter Reimers, Walter Reimers, M. Ionescu, M. Ionescu, M. Ionescu
PublisherTrans Tech Publications Ltd
Pages3876-3882
Number of pages7
ISBN (Print)0878492941, 9780878492947
DOIs
StatePublished - 2010
Externally publishedYes
Event6th International Conference on Processing and Manufacturing of Advanced Materials - THERMEC'2009 - Berlin, Germany
Duration: 25 Aug 200929 Aug 2009

Publication series

NameMaterials Science Forum
Volume638-642
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Conference

Conference6th International Conference on Processing and Manufacturing of Advanced Materials - THERMEC'2009
Country/TerritoryGermany
CityBerlin
Period25/08/0929/08/09

Keywords

  • Cu-Co-Ni granular alloys
  • Magnetic properties
  • Mechanical alloying

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