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

The present investigators previously found a new magnet alloy “Malcolloy” having a high coercive force in the system of cobalt and aluminum and then conducted studies on the influence of the additions of nickel, molybdenum, titanium and vanadium on their magnetic properties, the highest coercive force obtained being 1450∼1600 Oe. Further, they have investigated the influence of the addition of chromium on the properties of Co-Al alloys and have discovered that the coercive force and the maximum energy product of Co-Al alloys were increased generally by the addition of chromium. Thus, an alloy with the composition of 82.11%Co, 14.12%Al and 3.77%Cr shows a coercive force of 1450 Oe, a residual magnetic flux density of 3150 G and a maximum energy product of 1.42×106 G·Oe when tempered at 550°C for 15 hours after water-quenching from 1375°C, and the highest value of maximum energy product is 2.40×106 G·Oe. These alloys consist of many ferromagnetic elongated particles of about 300 Å in diameter which are dispersed in the matrix of nearly non-magnetic β′ phase. Consequently, it may be concluded that the high coercivity of these alloys is mainly caused by the existence of the small particles composed of a single magnetic domain.