EXPERIMENTAL INVESTIGATION ON THE ENTHALPIES OF FORMATION OF THE DYFE2, DYFE3, DY2FE17, ERFE2, AND ERFE3 INTERMETALLIC COMPOUNDS

The enthalpies of formation at 298.15 K for five intermetallic phases in the Fe-Dy and Fe-Er binary systems have been determined by indirect solution calorimetry in liquid aluminum at 1100 K. The phases were Fe 2Dy, Fe3Dy, and Fe17Dy2 in the Fe-Dy system and Fe2Er and Fe3Er in the Fe-Er system. The following mean values of Delta(f)H(298.15 K) are re ported: -11.1 kJ/mole for Fe2/3Dy1/3, -7.7 kJ/mole for Fe3/4Dy1/4, -1. 9 kJ/mole for Fe17/19Dy2/19, -12.5 kJ/mole for Fe2/3Er1/3, and -7.9 kJ /mole for Fe3/4Er1/4. The measured enthalpies of formation of the Fe2D y and Fe2Er compounds are almost equal, as are the enthalpies of forma tion of the Fe3Dy and Fe3Er compounds. The results are compared with e arlier experimental data, with values predicted by Miedema's semiempir ical method([1]) and with calculated results obtained by Colinet and P asturel([2]) using a tight binding model.