Coarsening of Cobalt Precipitates in Copper- Cobalt Alloys

Abstract

The Ostwald ripening of precipitates in Cu-Co alloys was investigated by electron microscopic observation. The variation of the mean particle radius ${\bar r}$, and the distribution of relative particle sizes, $f(r/\bar r)$, were obtained as functions of the aging time at 873K. The shape of $f(r/\bar r)$ was rather sharp and symmetrical around $r = \bar r$ in the early stage. It became broad with the aging and was similar, in the late stage, to the theoretical distribution of Ardell. It appeared that the shape of $f(r/\bar r)$ depends on the volume fraction but the growth rate of ${\bar r}$ scarcely depends on it. The rate of change of ${\bar r}$ was proportional to the cube root of the aging time from the early stage of aging.