Abstract
Since the present-investigators found new magnet alloy “Malcolloy” of high coercivity in the system of cobalt and aluminium, they have carried out studies of the effect of additions of nickel, molybdenum, titanium, vanadium and chromium on its magnetic properties and obtained the highest coercive force of 1600 Oe. Further, they have investigated the effect of the addition of tungsten on the permanent magnet properties of Co–Al alloys and discovered that the addition of tungsten increases the coercive force of the binary alloys. The alloy which exhibits the highest coercivity has the composition of 75.89% Co, 13.55% Al and 10.56% W and shows the coercive force of 1450 Oe, the residual magnetic flux density of 3100 G and the maximum energy product of 1.40×106 G·Oe when tempered at 525°C for 150 hours after water quenching from 1380°C. These alloys consist of many ferromagnetic elongated particles about 350 Å in diameter which are dispersed in the matrix of nearly nonmagnetic β′ phase. Consequently, it may be concluded that the high coercivity of these alloys is mainly caused by the presence of the fine particles of a single magnetic domain.
