Abstract
As already known, magnetic properties of Alnico permanent magnets can be improved by forming columnar crystals whose long axis are parallel to one of the ⟨100⟩ axis. In practice, chill iron plates are inserted in conventional baked sand moulds, to achieve the directional freezing in the casting. This procedure, however, is not yet satisfactory. A new method of producing a fully columnar crystal magnet, based on the zone melting plus the rapid directional cooling, has been described, which is named as “Zone Melting & Crystal Orientation Method” by the present writers. In this report, columnar crystal forming conditions and the possibility of production techniques have been examined and the effects of zone melting conditions such as the zone melting temperature, traveling rate and atmosphere have been studied. From the results of these studies, it is concluded that, if the suitable condition may be chosen, Alnico magnets made by this method have always a fully columnar crystal structure and excellent magnetic properties.
