Cold Workability and Magnetic Properties of FeCo–V Alloys With the Addition of a Small Amount of Al

Al oxide films are selectively formed on the surfaces of FeCo–V alloys with the addition of a small amount of Al by annealing under a low partial pressure of oxygen. The thickness of the oxide films increases with increasing Al contents and temperatures. The FeCo alloys have a brittle B2 structure at room temperature. The addition of V decreases the transition temperature from the bcc phase (A2-disordered structure) to the B2-ordered structure and heat treatment increases the ductility. In contrast, the addition of Al increases the transition temperature from the bcc to the B2, which inhibits workability. The transition temperature and magnetic properties of the FeCo–V alloys with small amounts of Al are further investigated. The endothermic and exothermic reactions of the Al-added FeCo–V alloys were determined by differential scanning calorimetry (DSC) to evaluate the transition temperature from the bcc to the B2 and from the fcc phase (A1 structure) to the bcc. The addition of a large amount of Al is shown to increase the order–disorder transformation temperature from the B2 to the bcc and deteriorates the cold workability. In addition, a large amount of Al is shown to reduce the magnetic flux density.