Solidification microstructure and phase constitution of Fe-7.5%Mo-16.5%Si ternary quasiperitectic alloy

Solidification of Fe-7.5%Mo-16.5%Si ternary quasiperitectic alloy is investigated by using differential scanning calorimetry (DSC) and drop tube containerless processing techniques. The primary phase is identified as R (Fe₅Mo₃Si₂) and the quasiperitectic phases are τ₁ (Fe₅MoSi₄) and Fe₃Si. With the decrease of droplet diameter, the cooling rate and undercooling of the droplets increase rapidly. The experiment result indicates that the solidification microstructure is composed of remnant primary phase, quasiperitectic phases and ternary eutectic when the droplet diameter exceeds 400 μm, whereas the ternary eutectic is suppressed when the droplet is smaller than 400 μm in diameter.