Masamichi Miki1 and Yoshikiyo Ogino1
1Department of the Materials Science, Himeji Institute of Technology, Himeji
The effect of Si addition on the nucleation and growth of the grain boundary cell in a Cu-10%Ni-8%Sn alloy on aging at 723 K after quenching from 1123 K were investigated by means of hardness measurements, optical and electron microscopic observations, and X-ray analysis. The addition of Si retarded the precipitation of the γ' phase in the matrix and suppressed the nucleation and growth of grain boundary cells. In the case of Si additions more than 0.4%, the cell was scarcely observed even after the long time aging. Very fine particles of Ni31Si12 phase were observed in the matrices and grain boundaries of the as-quenched specimens containing more than 0.4% of Si. Therefore, these fine particles in the grain boundaries must have occupied the nucleation sites of a γ ((Cu•Ni)3Sn) phase and resulted in the suppression of the nucleation of the cells which consisted of lamellar mixtures of the γ and α phases.
copper-nickel-tin alloy, cellular precipitation, grain boundary reaction, addition of silicon, age-hardening, grain boundary segregation, grain boundary precipitation, intermetallic compound, microstructure
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