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

Abstract

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°C at x(Cu) = 0.465at% and 1350°C 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.