Effect of the Copper on the Low Temperature Treatment of Al-Ni-Co Type Permanent Magnet

Abstract

It was found previously that the magnetic properties of Al-Ni-Co type N.K.S.-1F permanent magnets showed anomalies when heated at about 875°C and then cooled in the magnetic field (the low temperature treatment), and that the maximum energy product of these magnets subjected to this treatment is equivalent to or better than that by the high temperature (about 1300°C) treatment. The variation of optimum temperatures T_L for the low temperature treatment was already investigated in a series of the magnets containing various contents of Al, Ni and Co respectively. In this paper, the T_L was measured in a series of the magnets containing Cu up to 10%. The experiments show that the T_L decreases as the Cu content increases, and the gradient of T_L is 12.5°C per unit percent of Cu. At the same time the Curie points A₂ of these magnets were measured. A₂ decreases as the Cu content increases, but remains almost constant above about 3% of Cu. A₂ coincids with T_L at the standard composition of 3% Cu which shows the best magnetic properties, and A₂ is lower than T_L at a lower content of Cu and is higher at a higher content. The effect of the low temperature treatment is most excellent as the difference between A₂ and T_L is the smallest.