In order to consider the effect of cooling conditions on microstructure formation during casting of Cu–Ni–Si alloy (Corson alloy), the microstructures of
unidirectional solidification of the alloy were evaluated. Ingots of Corson alloy with several cooling conditions were prepared by Mizuta method, and microstructural
observations and analysis of the distribution of added elements were performed. The primary and secondary dendrite arm spacings (P–DAS and S–DAS) became
smaller with increasing cooling rate, and it was found that P–DAS and S–DAS can be accurately approximated by multiplier of cooling rate times temperature gradient,
and by that of cooling rate, respectively. Between secondary dendrites, Si was enriched from the initial solidification zone to the final solidification zone, and Ni was
almost constant around the initial solidification zone and enriched slightly around the final solidification zone. The Si enrichment was larger under the condition of
lower cooling rate, which is expected to be closer to the equilibrium state. In this study, it was found for Corson alloy that DAS became bigger and Si enrichment
between secondary dendrites was larger under the condition of lower cooling rate, and Ni enrichment was not affected by cooling rate.