Generalization of the results of metallographic, electron-microscopic, and X-ray diffraction studies in combination with the data of differential thermal analysis (DTA) enabled us to find general regularities in the sequence of the phase and structural transformations resulting in the formation of the single-phase gamma state in the course of solidification and subsequent cooling of ternary alloys based on the Ni3Al intermetallic compound, which depend on the substitution type intrinsic to a certain alloying element in the range of homogeneity of the gamma phase. A correlation was found between the substitution type preferable for a certain alloying transition element and the degree of localization of its valence d electrons, which can be characterized by the width of the d band (W-d) on the energy scale. The atoms of transition elements with a pronounced localization of d electrons substitute for nickel upon alloying. The higher the delocalization of the d electrons, the higher the ability of transition element to substitute for aluminum.