Abstract
Since the discovery of new magnet alloy “Malcolloy” having a high coercive force in the system of cobalt and aluminium, the present investigators have continued researches on the effect of additions of nickel, molybdenum, titanium, vanadium, chromium and tungsten on the properties of Malcolloy ; the highest coercive force obtained with each alloy is 1450 to 1600 Oe. In this report the effect of manganese addition on the properties of Co–Al alloys was examined, with the results that the coercive force of the alloys decreases and the residual flux density increases gradually with increasing manganese content: The maximum energy product shows the highest value in the alloy containing 84.59% Co, 12.81% Al and 2.60% Mn which exhibits a maximum energy product of 2.50×106 G·Oe, a residual flux density of 5900 G, and a coercive force of 860 Oe, when tempered at 525°C for 20 hours after water-quenching from 1375°C. These alloys consist of many ferromagnetic elongated particles about 350 Å in mean diameter which are dispersed in the matrix of the nearly nonmagnetic β′ phase. Consequently, it is considered that the high coercivity of the alloy is mainly due to the presence of the fine particles of a single magnetic domain.
