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A systematic investigation is made on the solid solution hardening of binary nickel alloys with additions of B-subgroup and transition metal elements. The 0.2% flow stress at 77 K and the Young's modulus are measured for a variety of binary alloys to evaluate the rate of solution hardening per one available data on the rate of change in lattice constant (da/dc), interpretation of the solution hardening that the hardening is more intense by the additions of transition metal elements than by the additions of B-subgroup elements where the hardening is linearly related with a combined parameter for the interaction between solute atoms and edge dislocations. Then the necessity is raised to carry out the similar type of investigation on the solution hardening of nickel in order to clarify whether the anomalous hardening effect is inherent in the Ll2 crystal structure of Ni3Al or in the majority component of nickel.Technological interest in nickel alloys has often centered on improving the heat resistant properties such as high temperature strength and creep strength by making alloys multicomponent. For this purpose, the additions of transition metals are generally accepted. Prominent examples are the modifications of commercial superalloys, in which the additions of those elements have been properly chosen utilizing regression analyses. As a more fundamental approach, the solid solution hardening has been studied in nickel binary alloys by a number of workers (2)- (9), however, the alloy

A systematic investigation is carried out on the temperature dependence of strength in ternary Ni3Al compounds with additions of transition metal elements. The rate of solid solution hardening per one with the rate of lattice parameter change, da/dc, although a linear correlation has been found for the addition of B-subgroup elements. The rate of change in activation energy to provide the anomalous positive temperature dependence of strength per one atomic percent of the solute, du/dc, is then evaluated. Together with the results for the addition of B-subgroup elements, the apparent valence is assigned for each transition metal element by an analogy utilizing equi-valence contour determined for B-subgroup elements. Then it becomes possible to discuss the relative magnitude of the mechanical anomaly in Ni3Al in terms of the phase stability concept of L12 phase, in which e/a ratio as well as the atomic radius ratio of the compound, RB/RA, as affected by ternary addition is an important parameter to alter the stability of the phase against other geometrically close packed phases. (Received August 9, 1985) Keywords shown that the characteristic mechanical anomaly of the compound is enhanced by such additions as to increase the electron-atom ratio and/or the atomic radius ratio of the compound. Then the rate of change in activation energy for the thermally activated process to provide the mechanical anomaly per one atomic percent of solute, dU/dc, has been evaluated for a variety of ternary alloying elements in relation to the valence difference between a ternary B-subgroup element andshown that the rate of solid solution hardening seems to be proportional to that of change in lattice parameter by additions of the Bsubgroup element, da/dc.In the present investigation, a similar strategy is extended toward evaluating the role of ternary additions of transition elements into the compound in its mechanical properties. Practically information on the effects of ter-

An attempt is made to interpret the solid solution hardening of Ni3Al alloys in terms of the elastic interaction between the strain fields of a dislocation and a solute. Ternary additions are made to the L12 intermetallic compound with both B-subgroup and transition metal elements which substitute for Al-sites. Young's modulus of the ternary alloys is measured and the rate of change in elastic constant per one atomic per cent of solute (dE/dc) is determined. With the available data for the rate of solution harden-

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