Fe-C合金融体の密度

抄録

Densities of molten Fe-C alloys were determined by the manometer method developed in a previous study. The density at 1873 K showed the minimum value at about 3.5 mol%C and the maximum value at about 6 mol%C. The change in volume expansivity with carbon content was similar to that of the density. The molar volume at 1873 K deviated slightly positively from the additive law in the concentration below 2.3 mol%C and negatively above 2.3 mol%C. The deviation at 2023 K or above that temperature was negative over the whole range of concentration except very low carbon content. The partial molar volumes of iron and carbon in the melts with carbon below 2.0 mol% and above 7.0 mol% were nearly equal to those of α and γ phase, respectively. The deviation of molar volume from ideal mixing was also compared with available information on the relation between the excess entropy of mixing and the volume change on mixing in binary iron alloy, and the interaction parameter between iron and carbon was deduced from the regular solution model. The results obtained could be explained by the speculation that the features of solid phase before melting remained in the short range order structure of the melts.