Abstract
High temperature thermodynamic properties of Fe-W alloys were studied by the use of Knudsen cell mass spectrometer. As this alloy system has only single volatile component, the internal standard method was utilized to obtain activities in alloys. By taking advantage of high melting point of Fe-W alloys, Fe was used as the standard material. In applying this technique, the effect of the height of sample surface in the cell on the ion intensity was taken into consideration. Samples were melted and solidified preliminarily in a Knudsen cell before each run and then iron foil was placed on the sample surface so that the change in the height of sample surface in the cell on melting during the measurement was minimized.
Activities and free energy and enthalpy of mixing were derived at 1873 and 1773 K. The following were obtained
γ°W(S)=7.6(±1.1), εWW=-2.2(±0.8), at 1873K
Values for the activities of Fe-Mo alloys were revised on the basis of the present knowledge about the influence of the height of sample surface on the ion intensity. The following values were obtained.
γ°Mo(S)=2.2(±0.17), εMoMo=-0.14(±0.18) at 1823K
