Abstract
In order to clarify an unsatisfactory hardening characteristic observed in some melts of commercial Cu-Be alloys, four kinds of specimens of similar composition were prepared; three of them were arranged as industrial scale experiments under different procedures assigned, the other specimen was imported as a commercial strip from Beryllium Corp’n U.S.A. The hardness changes with aging time were examined together by microscopic observation, and then discontinuous precipitation at the initial stage was observed by electron micrography. The results were as follows: (1) When aged at 310°C the specimen “Z” showed considerable rapid hardening at the initial stage, followed by rapid softening, whereas in the imported Alloy B no such trend was observed up to 6 hrs, and in the other two specimens slight but not serious softening was observed. (2) Overaging is associated with rapid initial hardening rate and with subsequent development of the nodules, which appeared as small semi-spheres or narrow bands at grain boundaries. (3) As aging proceeds the nodules spread into the matrix as well as along grain boundaries, then several nodules join together forming continuous net works around the grains. (4) At the advancing interface lamellar precipitates in the nodule are continuous with undercomposed matrix, but they break away from the matrix and sometimes spheroidize at the location apart from the interface.
