Experimental investigation on phase equilibria of the Nd-Y and Nd-Y-Fe systems

Phase equilibria of the Nd-Y system at 400, 600 and 800 °C and the Nd-Y-Fe system at 400 and 600 °C were investigated by X-ray diffraction (XRD) and electron probe microanalysis (EPMA). Based on the experimental results in this work and literature, phase diagram of the Nd-Y system was refined and isothermal sections of the Nd-Y-Fe system at 400 and 600 °C were constructed. In the Nd-Y system, the solid solubility range of δ(Nd₂Y) was approximately 28.66–36.85 at.% Y at 400 °C and a two-phase region (αNd)+(αY) was observed from 34.73 to 36.52 at.% Y at 800 °C. In the Nd-Y-Fe system, eight and six three-phase regions at 400 and 600 °C were determined, respectively. Two phases of Nd₂Fe₁₇ and Y₂Fe₁₇ link up with each other from the Nd-Fe side to the Y-Fe side across the isothermal sections at both 400 and 600 °C. The maximal solubilities of Nd in the Y₆Fe₂₃, YFe₃ and YFe₂ were about 13.13, 7.06 and 6.14 at.% at both 400 and 600 °C, respectively. There was also noticeable solubility of Y in Nd₅Fe₁₇ and Fe in (αNd) and δ(Nd₂Y) at 400 and 600 °C. In addition, three newly observed ternary compounds τ₁, τ₂ and τ₃ were determined with compositions of approximately 16.50 at.% Nd-16.50 at.% Y-67.00 at.% Fe, 15.00 at.% Nd-20.00 at.% Y-65.00 at.% Fe and 20.00 at.% Nd-15.00 at.% Y-65.00 at.% Fe, respectively.