The purpose of our research has been to improve the magnetic properties of Alnico powders for plastic bonded magnet. Here Alnico powders were produced by water-atomization instead of cast-crushing method as usual. An optimum heat treatment forpromotion of spinodal decomposition was obtained at 1000-1100K for a few minutes. Under these conditions, the magnetic properties were wholly improved, which were superior to cast-crushed Alnico powders. Practically the coercive force of both low-Co andhigh-Co water-atomized Alnico powders showed more than 600Oe and 1000Oe, respectively. Furthermore the additions of Co and Al were found to be effective for improvement of coercive force of both low-Co and High-Co Alnico powders. Water-atomization andsubsequent appropriate heat treatment enable Alnico powders to be lower-cost and higher-quality products than cast-crushed Alnico powders.
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