The relation between the composition and the physical and mechanical properties of heat treated copper base ternary alloys was investigated, and optinum relation in their composition, by which the electrical conductivity and the age-hardenability are especially improved, was found to exist as follows; the ratio of the content of nickel and beryllium in such alloys is nearly 5:1 in weight.
The diagrammatic consideration on the change of the electric conductivity and the age-hardenability due to the vari tion of the composition was carried out, and its relation was clarified; in such alloys as their both conductivity and age-hardenability can be significantly improved, the solid solubility change of the α-phase is not only large, but its purity after tempering becomes high, that is, its composition is gradually approached to the, pure copper by the precipitation of the ternary γ-phase. Besides this fact it must be noted that the ratio of the amount of α-phase to that of γ-phase is enlarged by the addition of small amount of nickel in berylliumcopper alloys, and that, accordingly, the formation of more amount of electrically good conductive α-phase than that in the other alloys can be attained. The results of tensile and impact tests on 0.2% Be-Ni-Cu alloys were also shown. The large variation of the grain size of quenched alloys as well as the age-hardenability by tempering may be the chief causes of the change in impact or elongation values of tempered alloys. The cause of the grain refinement of 0.2% Be-Ni-Cu alloys with the increase in nickel was also considered.