Effect of the Nickel Content on the Low Temperature Treatment of Al-Ni-Co Permanent Magnets

Abstract

It was found previously that the magnetic properties of Al-Ni-Co type N.K.S.-1F permanent magnets show anomalies when heated at about 875°C and then field cooled, and the maximum energy product of this magnet alloy thus treated is the same as or better than that by the high temperature treatment. The variation in the temperature of the low heat treatment was investigated in a series of magnet alloys containing various Ni contents. This paper deals with the variation in the low heat treatment when measured a series of magnet alloys with 12 to 20% Ni contents. The experiments show that the temperature of the low heat treatment decreases as the Ni content increases, and the gradient of variation is about 22.6°C per unit %Ni. The curie points of these magnets measured at the same time are almost constant, and coincides with the temperature of the low heat treatment T_L at the standard composition of 16%Ni; it becomes lower than T_L with decrease of the Ni content and higher with increase of the Ni content. It is assumed that the effect of the low heat treatment is most effective when the difference between curie points and T_L is the smallest.