PHASE-EQUILIBRIA IN THE TERNARY HO-FE-ND SYSTEM AT 500 DEGREES-C

The solid state phase equilibria and phase relationship in the ternary Ho-Fe-Nd system at 500 degrees C were investigated mainly by X-ray po wder diffraction and by differential thermal microanalysis. The isothe rmal section at 500 degrees C of this system has been established. The existence of the binary compounds Fe17Nd5 in the Fe-Nd system and the delta phase (Sm type) in the He-Nd system were confirmed. The delta p hase belongs to the rhombohedral system with a = 0.3636 nm and c = 261 46 nm in the hexagonal description. The composition range of the delta phase is from 45 to 65 at.% Nd. The isothermal section consists of ni ne single-phase regions, 15 two-phase regions and six three-phase regi ons. The compounds Fe17Nd2 and Fe17Ho2 form a continuous series of sol id solutions. At 500 degrees C, the solid solubilities of Fe in alpha- Ho, alpha-Nd or the delta phase are small and Fe17Nd5, Fe23Ho6, Fe3Ho and Fe3Ho are non-variable compounds.