Abstract
An investigation on the γ/γ' phase equilibria with particular emphasis or γ solvus is carried out in ternary Ni-Al-X systems with X being one of the VIA transition metal elements, Cr, Mo, or W. Differential thermal analysis (DTA) is employed as a key experimental technique, which is not very common to be used for the determination of phase boundaries. It is superior to the conventional methods because γ solvus surface with respect to ternary composition and temperature is readily obtained. The results obtained in each ternary system seem to be consistent and accurate, by which a large discrepancy is in many cases pointed out upon comparisons with the information reported in the past. An advanced analytical method, SEM-EDX, not only confirms the results obtained on γ solvus but also provides solid evidences for the occurrence of a four phase equilibrium in Ni-Al-Cr and in Ni-Al-Mo systems which is suggested by the results of DTA.
