The microstructure and properties of equiatomic iron-cobalt magnetic alloys with alloying additions

The structural factors controlling the magnetic and mechanical properties of FeCo alloys near the equiatomic composition were investigated and the effects of additions of up to 5 at. % of Si, Ni, Cu, W to FeCo and FeCo2V alloys are described. The magnetic performance of commercial FeCo2V alloys was found to be principally determined by the recrystallised grain size, and its control could be effected by various thermo-mechanical treatments. Such treatments cause the material to develop a preferred crystallographic orientation in both the cold-rolled, and rolled and annealed conditions. The recrystallisation textures are related to the observed magnetic performance. A method is described by which the long-range order parameter can be calculated by observation of the order induced changes in the lattice parameter. It is shown that the reliability of quenched FeCo alloys is determined principally by the degree of long-range order and that the beneficial effect of vanadium is due to the retardation of the ordering reaction. Of the alloys studied tungsten, nickel and copper also retarded the ordering reaction, although to a lesser degree than vanadium, whilst silicon additions promoted the reaction. Most of the alloy additions caused precipitation of various secondary phases and these effect the magnetic and mechanical properties. The magnetic properties of the ternary and quaternary alloys were poorer, but not markedly so, than those of FeCo2V. However some of the additions also improved the ductility in the finished ordered state. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DX212746 / BLDSC - British Library Document Supply CentreGBUnited Kingdo