Effect of liquid–liquid structure transition on the nucleation in undercooled Co–Sn eutectic alloy

•A critical overheating temperature is found at 1310 ± 10 °C in Co-24 at% alloy.•The undercooling of the alloy is significantly affected by the overheating.•The liquid–liquid structural transition is considered to be the factor to cause the sharp increase of undercooling.•The liquid–liquid structural transition may alter the wetting angle according to the classic nucleation theory.

The effect of liquid–liquid structural transition (LLST) on the undercoolability of liquid Co–Sn eutectic alloy has been investigated via cyclic overheating and undercooling. Results show that the stable undercooling increases considerably when the melt is overheated above a critical overheating temperature. The LLST is evidenced by differential scanning calorimetry (DSC) experiment and is thought to be the major factor for the sharp increase of undercooling at the critical point. The effect of LLST on undercooling is analyzed quantitatively within classical nucleation theory.