Relation between magnetic properties and crystallographic texture of columnar Alnico 8 permanent magnets

The purpose of this work is to correlate solidification rate during a controlled cooling and magnetic properties of columnar Alnico 8 or Ticonal 1500 (Al 7.5%, Ni 14%, Co 35%, Cu 3%, Ti 4.3%, Nb 1.2%, Fe bal). Our investigations involved a controlled solidification with vertical zone melting furnace, micrographic examinations of the specimens, and magnetic measurements of the specific energy product, . In order to study the texture of the different samples we have carried out X-ray diffraction experiments using SCHULZE\´s method, with an automatic pole figure recorder developped by RUER. At freezing rate of 0.7 cm/hr and a temperature gradient of about 150 K/cm we obtain single crystal structure. For medium freezing rate the samples show dendritic structures with disappear utterly after heat treatments. The dendritic grains may have various orientations. For high freezing rates (> 9 cm/hr) the crystals are well oriented : the <100> directions are parallel to the sample longitudinal axis. After heat treatment the specific energy product reaches 10 MG.Oe ; ( kJ/m³.