Experimental Investigation of Phase Equilibria in the Y-Co-Cu Ternary System

Abstract

The phase equilibria of the Y-Co-Cu ternary system were investigated experimentally by scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction. The experimental results did not indicate any ternary intermetallic compounds and revealed that the YCo₅ and YCu₆ binary intermetallic compounds form the continuous solid solution phase Y(Co, Cu)₅ because of having the same space groups. According to the measured phase compositions at 873 K, the solid solubilities of Co in fcc(Cu), YCu₄, Y₂Cu₇ and YCu₂ are 8.6, 1.7, 44.0 and 8.6 at.%, respectively, while those of Cu in fcc(Co), Y₂Co₁₇, Y₂Co₇, YCo₃, YCo₂, Y₂Co₃, Y₆Co₇, Y₄Co₃, Y₈Co₅ and Y₃Co were determined to be 15.8, 6.4, 8.1, 13.5, 7.9, 1.2, 1.4, 3.9, 7.6 and 10.6 at.%, respectively. Furthermore, at 1073 K the solid solubilities of Co in fcc(Cu), YCu₄, Y₂Cu₇ and YCu₂ were measured to be 3.9, 2.5, 40.0 and 10.8 at.%, respectively, while those of Cu in fcc(Co), Y₂Co₁₇, Y₂Co₇, YCo₃, YCo₂, Y₂Co₃ and YCo were determined to be 13.6, 9.4, 7.4, 13.7, 10.3, 2.3 and 31.4 at.%, respectively. Two isothermal sections of the Y-Co-Cu ternary system at 1073 K and 873 K were established finally.