Effect of Germanium Additions on the Properties of “Malcolloy” in the System of Cobalt and Aluminium

Abstract

Since the discovery of “Malcolloy” having high coercive forces in the system of cobalt and aluminium, investigations have been made on the effect of additions of nickel, molybdenum, titanium, vanadium, chromium, tungsten and manganese on the properties of Malcolloy, the highest coercive force obtained in each system of alloys being 1200∼1600 Oe. In this report, the effect of germanium additions on the properties of Co–Al alloys is examined, with the result that the coercive force of the alloys increases with increasing germanium content. An alloy composed of 81.80% Co, 9.20% Al and 9.00% Ge shows a coercive force of 1600 Oe, a residual magnetic flux density of 4200 G and a maximum energy product of 2.20 MG . Oe when tempered at 500°C for 125 hr after water-quenching from 1310°C. These alloys consist of many ferromagnetic elongated particles about 500∼1500 Å in length which are precipitated in the matrix of the nearly nonmagnetic β′ phase. The results show that the high coercivity of these alloys is mainly caused by the presence of single magnetic domain particles.