Distribution equilibria of iron and nickel in two phase fields of the Fe-Ni-B system

The crystallographic characteristics and the equilibrium ratios for solid solutions containing 33 and 50 at% boron which belong to the Fe-Ni-B system are described. The study was carried out on samples obtained by diffusion at 1073 K, of mixtures of the elements in powder form. It was possible to confirm the existence of a complete solid solution between the compounds Fe2B and Ni2B. On the other hand, there are two solid solutions containing 50 at% boron: one is derived from the compound FeB in which up to 70% of the iron atoms can be substituted by nickel, the other derives from the boride NiB and extends as far as the component (Ni0.85Fe0.15)B. Curves were obtained indicating the variation of lattice parameters and volume of the respective elementary cells with composition for these solid solutions. The different insertion of nickel in the borides was also quantified and the relative limit distribution coefficient was evaluated. Its value is consistent with those calculated on analogous borides of transition elements at the same temperature.