珪素青銅の恒温過冷変態

Abstract

The changes in structure during the isothermal transformation at the temperature of 500° and 400° for 4.75%, 4.97%, and 5.50% Si-Cu alloys quenched from 800° were tested microscopically. The transformation proceed very slowly from the initial state, α for 4.75% and 4.97% Si-Cu alloys and α+κ for 5.50% Si-Cu alloy, to the most stable equilibrium state α+γ through the meta-stable equilibrium state between α and κ, as shown in Fig. I extending the boundary lines α⁄α+κ and α+κ⁄κ to the lower ranges of temperature. It was considered that the slow phase change of α to κ on quenching into a region of temperature of about 400° where it whould be stable as κ, i.e., beneath the extension of the line α+κ⁄κ, is of diffusionless “nucleation and growth” type.