Calculation of constitution of nickel base superalloys by cluster variation method

High temperature performance of nickel-base superalloys vitally depends on the constitution of alloys, i.e. volume fraction and composition etc. of constituent phases. The development of computer models to predict the effects of multiple alloying additions on the alloy constitution may facilitate the designing of alloys and lead to further improvement of high temperature performance. Some of the present authors have demonstrated that the cluster variation method with tetrahedron approximation which utilizes the Lennard-Jones pair potential can predict satisfactorily various characteristics of γ′/γ equilibrium in Ni-Al alloys containing one or two alloying elements without excessively increasing the computational load. In this study, calculations are extended to some practical and experimental multicomponent alloys and the results are compared with experimental data on the volume fraction and composition of γ′ and γ phases, lattice misfit and site occupation of alloying elements in the γ′ lattice. In the present form the model can be used to calculate the constitution of single crystal superalloys in which no interstitial trace elements such as carbon and boron are added to prevent grain boundary embrittlement.