One method by which the efficiency of gas turbine engines may be improved is by increasing the gas stream temperature on entry to the turbine. Currently this temperature is limited by the thermal stability and strength of the materials used for the turbine blade and disc components, namely nickel-base superalloys. One class of materials that is being considered as potential successors are alloys strengthened with intermetallic compounds other than Ni3Al. In this study, neutron diffraction will be used to characterise the phases that are formed in a series of alloys from the Co-Ni-Al-Ti quaternary system. From the data that is obtained, the extent of the L12 phase field between Ni3Al to Co3Ti will be determined.