The Change of Magnetic Properties of Alnico-5 Magnet by Heating at 300∼500°C

Abstract

The magnetic properties of the completely heat-treated Alnico-5 magnet were not changed by heating at 300∼500°C. During heating at 300∼400°C in an incompletely aged Alnico-5 magnet, the coercive force was decreased about 10%, but the residual induction increased about 3%. These changes were also observed in the other Alnicos. It is assumed that the decrease of coercive force during heat exposure to temperatures below 450°C is due to the transformation of slightly retained γ-phase to α-phase. The increase of coercive force is due to the decomposition of α-phase to α₁+α₂ phases.