A thermodynamic assessment of the nickel–lead system

Thermodynamic properties and the phase equilibria of the Ni–Pb binary system were assessed by the CALPHAD (CALculation of PHase Diagrams) method using the available literature data. The phase diagram and the excess Gibbs energy values of the solution phases, molten alloy and the fcc solid solution were modelled using the Redlich–Kister polynomials. The experimental data was fitted by a least squares method using MTDATA software tool.The upper consolute point of the liquid miscibility gap was calculated to be at 1804.8 K at 27.23 at.% Pb. The monotectic equilibrium was calculated between the fcc nickel solution at 0.13 at.% Pb, the nickel-rich end of the liquid miscibility gap at 11.91 at.% Pb and its lead-rich end at 59.65 at.% Pb at a temperature 1626.5 K. The eutectic equilibrium was calculated between an fcc nickel solution containing 0.02 at.% Pb, the eutectic liquid at 99.62 at.% Pb and a lead-rich fcc solution containing 99.98 at.% Pb at a temperature 598.3 K. Agreement between the assessed phase diagram and the experimental values is very good.