Solidification pathways of ternary Cu62.5Fe27.5Sn10 alloy modulated through liquid undercooling and containerless processing

The active control of microstructure evoluztion is still a challenging factor for the development of advanced immiscible alloys. Here, we make an attempt to modulate the solidification pathways of undercooled Cu62.5Fe27.5Sn10 alloy by glass fluxing and drop tube techniques. Through regulating the liquid undercooling, three types of microstructures, dendrite, dispersive structure and macrosegregation pattern, were formed under the normal gravity condition. Below the first critical undercooling of 15 K, the alloy melt displayed the normal peritectic solidification. At moderate undercoolings above 15 K, the metastable liquid phase separation took place and the solidified microstructure appeared as homogeneously dispersed structure. If undercooling further overtook the second threshold of 107 K, macrosegregation occurred and the bulk alloy separated into an Fe-rich zone and a Cu-rich zone. Under the free fall condition, the alloy droplets with the droplet diameter beyond 805 mu m showed the equilibrium peritectic solidification. If the droplet diameter decreased below 805 mu m, the metastable liquid phase separation was induced and the microstructural morphology of Cu62.5Fe27.5Sn10 alloy droplet evolved from dendrite into dispersive structure. Furthermore, experimental and simulated results revealed that the temperature gradient had great influence on the size distribution of Fe-rich globules.