Phase Equilibria in Ni-Rich Portion of Ni-Si System

The phase equilibria of the Ni-rich portion in the Ni-Si system were investigated. The phase boundaries between liquid and fcc phases were established by the diffusion couple method and those of fcc and β1 or β2 were determined by the SEM-EDX measurement of two-phase alloys. The liquidus of the present work well agrees with the previous experimental data determined by a thermal analysis. The solidus data are rather different from the previous experimental data, but agree with the thermodynamic calculated phase diagram. This result suggests that the present solidus and liquidus data are consistent with thermodynamic data. The solubility of Si in the fcc phase agrees with some previous experimental data, but disagrees with the thermodynamic calculated phase diagram. This fact suggests that the thermodynamic reassessment for this system is necessary by the CALPHAD approach.