Abstract
The Silicon-bronze, Cu-Zn-Si-alloy, which was developed by Dr. Tokiji Isikawa is comparatively light. strong and non-corrosible, and has many advantages as a substitute alloy for Tin-bronze. However, by annealing at 300_??_500°, it shows frailty, decreasing a shock value and elongation, increasing hardness, and yet almost does not change tensile strength. At the temperature of that range, the higher the temperature and the longer the times of annealing, the more brittle the alloy becomes. By the author's experimental results, when the alloy is annealed for a long time at the temperature of, 300_??_100°, it has become brittle. This is attributed to precipitation of γ phase in the grain boundary of a phase by decreasing solubility of Si in the α phase due to the addition of Zn. This precipitation could not be prevented by adding other. elements to the alloy. From the microscopic structures, the solubility of Si at 250° in Cu-Zn-alloys was found to be extremely smaller than that given in the former researches. Therefore it is concluded that the Silzin-bronze can be used only in the parts which require strength and non-corrosibility but not in the parts which are heated by steam, etc.
