Factors affecting the magnetic properties of alloys fine dispersions of cobalt.
The properties of many permanent magnet materials are due to the presence of a finely divided ferromagnetic phase which, in some cases, contains a substantial proportion of cobalt. The most important examples are the alnico alloys, deriving permanent magnet properties from a fine dispersion of a ferromagnetic, b.c.c. phase rich in cobalt and iron. This thesis is concerned with the magnetic properties of alloys in which the ferromagnetic dispersion is essentially pure cobalt. A large part of the work consists of an examination of an established group of permanent magnet materials, the binary cobalt aluminium alloys known as Malcolloy, in which cobalt is precipitated from super-saturated solid solution during heat treatment. The properties of an alloy in the cobalt titanium system, in which a cobalt precipitate can be induced by a similar process, are also considered and the possibility of producing sufficiently fine dispersions by the eutectic and eutectoid reactions occurring in several binary cobalt alloy systems is examined. In the course of the investigations various magnetic parameters have been studied and it is perhaps useful, at this stage, to define these and to comment on their significance. Much more detailed discussions of the fundamental basis from which magnetic quantities and properties are derived, the units in which they are measured and the symbols by which they are conventionally represented have been presented by a number of authors.
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Sheffield Hallam University (United Kingdom).