Near equiatomic FeCo alloys: Constitution, mechanical and magnetic properties

This review attempts to summarise the current knowledge about the constitution, mechanical and magnetic properties of these alloys, focussing on the general properties of bulk FeCo and FeCo-X alloys (developed for applications such as rotor or stator laminations in motors). Recent development of nanocomposite and nanocrystalline materials such as HITPERM are not considered. A review of this developments is available in [McHenry ME, Willard MA, Laughlin DE. Amorphous and nanocrystalline materials for applications as soft magnets. Prog Mater Sci 1999;44:291-433]. An overview is given of work undertaken to date on various FeCo-X ternary system, with emphasis on the influence of these ternary additions on microstructure and characteristics of the phase diagram. The problem of the kinetics of ordering is given particular attention. Magnetic and mechanical properties are then discussed with emphasis on the relationship between microstructure and properties, and the main quantitative theories put forward are assessed again data gathered from the literature. It is shown that, while some points are clearly understood, a number of question remains in different areas which are outlined.