Association in ternary metallic melts Fe–Mn–Si, Fe–Cr–P and Fe–Mn–P

Abstract

Knudsen-cell mass-spectrometry was used to investigate the thermodynamic properties of liquid alloys Fe–Mn–Si (1435–1809 K), Fe–Cr–P (1403–1821 K) and Fe–Mn–P (1302–1701 K). Niobium or molybdenum double effusion cells with inner surfaces covered with ZrO 2 or Al 2O 3 were used in the experiments. Nickel, copper, chromium or strontium fluoride served as a reference substance. The saturated vapor was found to consist mainly of atoms Fe, Mn, Cr, Si, P and molecules P 2, Si 2. Representative files of data comprising 700, 1100, and 1500 values of activities of all components were received for the Fe–Mn–P, Fe–Cr–P and Fe–Mn–Si liquid solutions. The thermodynamic properties of the melts were approximated by the associated-solution model. For adequate representation of the experimental data it was necessary to take into account the binary associates, formed by iron, chromium and manganese atoms with silicon or phosphorus, ternary associative complexes FeMnSi, FeCrP or FeMnP and excessive terms describing interactions between monomer species. The thermodynamic characteristics of the binary associates were found to agree within the limits of experimental error with the values established earlier from the experimental data for binary systems.