Abstract
The atomic size of each element in age-hardenable alloys has an important effect upon age-hardening. The author has studied various cases of ternary alloys and proposes the following hypothesis. The solubility surface of ternary alloy is the most promising for age-hardening and when the atomic radius of one solute is larger and the other is smaller than that of the solvent and these differences in atomic size between each solute and the solvent are almost the same, the alloy may be expected to have the largest ratio of age-hardening. Furthermore the larger the difference is, the harder-is the alloy obtained. Such alloys like duralumin and C-alloy satisfy the hypothesis completely. The system of Cu-Be-Ti seems to be one of the alloys of this type. Ten samples of the alloys whose compositions lie for on the line of 8.4 atom% solute in the equilibrium diagram were examined for their distribution curve of quenched hardness. And there emerged that the distribution curve of quenched hardness showed the minimum point at the composition of Ti, 4.0 atom% and Be, 4.4 atom%, and the distribution curve of tempered hardness gave the maximum at the same point. The ratio of the age-hardening of the sample was as much as 225% and it is about the same as C-alloy. From the results, therefore, one more example was found to which also the above mentioned hypothesis was applicable. The distribution of lattice constants in the α phase can be shown as an inclined plane involing two Vegard lines, and a handy nomograph which explains the relation between the distribution and the composition is proposed.
