Refinement of the γ phase with melt undercooling in a two-phase Co2NiGa magnetic shape memory alloy

The effect of melt undercooling on the γ phase is investigated in a two-phase Co2NiGa magnetic shape memory alloy by employing the method of glass fluxing combined with superheating cycling. A maximum bulk undercooling of 230 K is achieved. Microstructural evolution of the Co2NiGa alloy is investigated by optical microscopy with respect to different degrees of undercooling. Over the whole range of undercooling, it is found that both the size and the volume fraction of the γ phase are drastically influenced by undercooling. Especially, when the undercooling is in the range of 190–230 K, the alloy has an obvious preferred orientation.