High Temperature Phase Relations in Ni–RE(RE=La, Ce, Pr, Nd) Binary and Ternary Alloy Systems

Abstract

The liquidus lines of the RE-rich side which are in equilibrium with solid compounds Ni₅RE in the four Ni–RE (RE=La, Ce, Pr, Nd) systems or in equilibrium with solid compounds Ni₅RE_j,θRE_k,(1−θ) (RE_j and RE_k represent any two of the rare earths from La, Ce, Pr and Nd) in the six Ni–RE_j–RE_k ternary systems were determined experimentally in a temperature range of 1273∼1513 K. On the basis of the phase relations obtained and the available thermodynamic information, a thermodynamic evaluation was carried out for the Ni–RE binary and Ni–RE_j–RE_k ternary systems in order to derive a set of coefficients which describe the free energy of mixing of the liquid phases as a function of composition and temperature. Using the free energy of mixing, phase relations were predicted for the Ni–RE binary and Ni–RE_j–RE_k ternary alloy systems at temperatures above 1513 K and at high concentrations of nickel above X_Ni=0.833 (Ni₅RE).