Thermodynamic study of phase equilibria in the Ni-Si-B system

A thermodynamic analysis of the phase equilibria in the Ni-Si-B ternary system was conducted. A regular solution approximation based on a sublattice model was adopted to describe the Gibbs energies for the individual phases in the binary and ternary systems. A set of thermodynamic parameters for the individual phases was evaluated from literature data on phase boundaries and thermochemical properties. The optimized parameters reproduced the experimental data, for the most part, satisfactorily. However; in the calculated isothemal section at 850 degreesC, phase equilibria between the fee phase and Ni6Si2B or Ni3Si(beta (1)) and Ni6Si2B were found instead of the experimentally observed equilibria between Ni3Si(beta (1)) and Ni3B or Ni5Si2(gamma) and Ni3B. Further, in the primary crystal surface for the fee phase, the calculated liquidus temperatures were higher than the reported values by approximately 80 degreesC, Therefore, it is considered that the fee phase evaluated in the Ni-Si system by Lindholm and Sundman is too stable.