Effect of the Chromium Addition on Properties of New Magnet Alloy “Malcolloy” in the System of Cobalt and Aluminium

Abstract

Following the discovery of new magnet alloy “Malcolloy” of high coercivity in the Co–Al system, the present authors have made a series of experiments on the effect of the addition of nickel, molybdenum, titanium and vanadium on properties of Co–Al alloys, and obtained the highest coercive forces of 1450∼1600 Oe. Further, they have found that the coercive force and the maximum energy product of Co–Al alloys are generally increased by the addition of chromium: An alloy composed of 82.11% Co, 14.12% Al and 3.77% Cr shows the coercive force of 1450 Oe, the residual magnetic flux density of 3150 G and the maximum energy product of 1.42×106 G·Oe when tempered at 550°C for 15 hrs after water-quenching from 1375°C. The highest maximum energy product among all the alloys studied is 2.40×106 G·Oe. Such high-coercivity alloys consist of many elongated particles of a ferromagnetic phase, about 300 in diameter, dispersed in the matrix of a nearly nonmagnetic β′ phase, from which it is apparent that their high coercivity is mainly due to the presence of the fine particles of a single magnetic domain.