Effect of Denucleating Techniques on Undercooling of Co₂NiGa Alloys

Abstract

By using the method of glass fluxing combined with superheating-cooling cycling, the undercooling behaviour of Co₂NiGa alloy melts was investigated. The obtained degree of undercooling is very different with differently used glass due to different denucleating mechanisms. The denucleating agent composed by 70% Na₂B₄O₇ + 30% NaSiCa showing a moderate viscosity and good physicochemical purification ability was optimized to be an ideal denucleating agent. By using this kind of denucleating agent, a large (>200 K) and stable undercooling can be obtained in Co₂NiGa melts after superheating over 200 K for 1.5 min. The effects of the superheating and holding time on undercooling have been discussed.