Overheating dependent undercooling in a hypoeutectic Co–B alloy

• A characteristic overheating temperature around 1390 °C is determined in Co83B17 melt.
• The mean undercooling was strongly affected by the characteristic overheating temperature.
• Liquid–liquid phase transition around 1390 °C was the main reason for the overheating dependent undercooling.
• In-situ magnetization measurement can detect structure transition in liquid metals.

The effect of overheating on the undercooling behavior of a hypoeutectic Co–B alloy has been studied by molten glass fluxing combined with thermal cycling method. Results indicate that the undercooling of Co83B17 alloy is greatly affected by the overheating temperature and a critical threshold temperature is determined. The existence of the turning point is thought to be related with the structure transitions inside the overheated liquid which is confirmed by in-situ high temperature magnetic measurement.