Abstract
The hardness of cold-worked alpha-brass increases, if it is annealed at the temperatures below recrystallization temperature. This hardening phenomenon is a sort of strain age-hardening. The hardening curves at constant temperatures are hyperbolic in type. This age-hardening, therefore, must be the one which should be called the pseudo-precipitation type(it was called the non-precipitation type, in the preceding paper, this journal, Vol. 12, No. 7-12, p. 16, 1948), or which is caused by the formation of Guinier-Preston aggregates. Concerning the reason of this idea, the readers are refered to the preceding paper (loc. cit.). The activation energy of the strain age-hardening process of alpha-brass is 20000 cal/mol, which is very much smaller than the activation energy of diffusion of zinc atoms in alpha-brass.
