Semihard Magnetic Alloys of Co–Fe–Nb System

Ductile alloys of the Co–Fe–Nb system in the vicinity of 90% Co were studied for reed switch applications. Wires have been investigated which have high values of coercive force, squareness ratio and remanence as well as high stability of these magnetic properties against heating. As a result of this research, an 85 Co–12Fe–3Nb wire, 0.5 mm in diam., subjected to a sequence of a 1100°C intermediate anneal, 90% cold reduction and 750°C aging is deemed best for this application. This wire shows a coercive force of 20 Oe, a squareness ratio of 0.95 and a remanence of 15 000 G. Intermetallic Co–Nb compounds precipitate during aging treatment. This phenomenon causes the coercive force to increase. The cold drawing facilitates the precipitation. The intermediate anneal temperature should be sufficiently high to realize a complete solid solution in the wire. The drawn wire has $\text{〈111〉}$ fiber texture. Since $\text{〈111〉}$ is an easy magnetization direction, the wire shows a good rectangular hysteresis loop along the axis. This texture remains the same up to 900°C anneal. Some wires of these alloys are used for semihard magnetic reed switches in various electronic equipment such as control devices and electronic switching systems.