Supercooling, isothermal soaking and liquid phase separation of Cu-Co alloys

In this paper, liquid phase separation of Cu₇₅Co₂₅ and Cu₈₅Co₁₅ alloys has been investigated during isothermal soaking at different supercooling rates. The results reveal that the liquid phase separation occurring during isothermal soaking can develop to a relatively large extent compared with continuous rapid cooling, resulting in larger quantities and larger sizes of Co-rich particles. The primary dendrites formed at small supercoolings tend to re-dissolve into the Cu-rich liquid and shrink locally in size leading to dendrites that break into segments. These dendrites and their small segments can collide with each other under the action of the electromagnetic force during high frequency induction heating and accumulate to form large Co-rich particles. It is found that whether the Co-rich droplets from the liquid separation solidify or not depends on the extent of the liquid phase separation at fixed temperature. Once the composition of Co-rich liquid reaches to the miscibility gap borderline, solidification can immediately take place.