Effect of Molybdenum Addition on the Properties of a New Magnet Alloy “Malcolloy” in the Co–Al System

Abstract

Four years ago the present authors discovered a new magnet alloy “Malcolloy” having a high coercive force, and determined the effect of nickel additions on its properties, the highest coercive force thus obtained being 1500 Oe. In this paper, the effect of molybdenum addition on the properties of Co–Al alloys, has been studied and found that the coercive force of the alloys increases generally by the addition of molybdenum: An alloy containing 80.51% cobalt, 13.96% aluminium and 5.53% molybdenum shows a coercive force of 1600 Oe, a residual magnetic flux density of 2750 G and maximum energy product of 1.34×106 G·Oe, when tempered at 600°C for 20 hr after water-quenching from 1380°C. These alloys consist of many ferromagnetic elongated particles about 400 Å in mean diameter which are dispersed in the matrix of a nearly nonmagnetic β′ phase. Therefore, it may be concluded that the high coercivity of these alloys is mainly due to the presence of the fine particles of a single magnetic domain.