THERMODYNAMIC PROPERTIES OF (XFE-X-Y)SI)(1) AND (XFE+YMN+(1-X-Y)P)(1)(YMN+(1)

A Knudsen effusion technique combined with mass-spectrometric analysis of the evaporated products has been used to investigate the gaseous p hase and to determine the thermodynamic properties of {xFe+yMn+(1-x-y) Si}(I) in the temperature range 1435 K to 1823 K and of {xFe+yMn+(1-x- y)P}(I) in the temperature range 1302 K to 1701 K. Concentrations of t he components varied within the mole-fraction ranges x, 0 to 1; y, 0 t o 0.6; and (1-x-y), 0 to 1 in the first system, and x, 0.205 to 0.738; y, 0.22 to 0.695; and (1-x-y), 0.152 to 0.365 in the second. The isoa ctivity lines of silicon and phosphorus are close to the secants conne cting the Fe-Si and Mn-Si, Fe-P and Mn-P binary sides. Iron and mangan ese activities decrease regularly as the configuration point runs from {xFe+(1-x)Mn}(I), towards {xFe+(1-x)Si}(I) or {yMn+(1-y)Si}(I), and t owards {xFe+(1-x)P}(I) or {yMn+(1-y)P}(I). The thermodynamic propertie s have been described with the associated-solution model assuming that binary and ternary complexes exist in the melt. (C) 1996 Academic Pre ss Limited