Further development of Ni-base superalloys based on γ–γ′ structures offers little hope of substantial improvements in properties for gas turbine applications. However because of the substantial technology base which exists for nickel base alloys there are considerable advantages, in research time and money, in developing new nickel base alloys. Interest in the 1970's in directionally solidified composites indicated some possible new systems to replace γ–γ′ alloys. More recently there has been renewed interest in aluminides such as FeAl, CoAl and NiAl. These materials exhibit melting points which are substantially greater than for current γ–γ′ alloys. Problems of lack of ductility for these alloys may be resolved by alloying and novel processing routes such as rapid solidification.

In addition to NiAl there are a number of other nickel intermetallics which from limited experimental data are worth considering at least as second phases. Some of these compounds are Ni7Hf2, Ni7Zr2, Ni5Zr, Ni6A1Ta and Heusler alloys of the type NiAlx where x is a transition element. The solubilities and phase relationships and where available the mechanical property data in a number of nickel ternary systems will be reviewed in terms of their potential for development of new high temperature alloys.