Investigation of the stable and the metastable liquidus miscibility gaps in Fe-Sn and Fe-Cu binary systems

Two kinds of experimental methods were tried in the present work:(i) the powder metallurgy method combined with differential thermal analysis (DTA) to determine the metastable liquidus miscibility gap for a Fe-Cu binary system and (ii) the high-temperature melting method combined with isothermal treatment to determine the stable liquidus miscibility gap for a Fe-Sn binary system. The experimental method was adopted according to the characteristics of the liquidus miscibility gap of the specific system. Using the powder metallurgy method, a uniform microstructure morphology and chemical composition was obtained in the DTA specimen, and the phase-separation temperature of the supercooled metastable liquid was measured. The isothermal treatment was applied for the samples inside the stable liquidus miscibility gap; here, equilibrated compositions were reached, and a layered morphology was formed after rapid cooling. The liquid miscibility gaps of the Fe-Cu and Fe-Sn binary systems were measured, and the peak temperatures of the corresponding miscibility gaps were determined to be about 1417℃ at x(Cu)=0.465at% and 1350℃ at x(Sn)=0.487at%, respectively. On the basis of the experimental results, both the Fe-Cu and the Fe-Sn binary systems were thermodynamically assessed.