Experimental study of phase equilibria in Y–Co–Zr system at 600 °C and 800 °C

Abstract

Phase equilibria of the Y–Co–Zr ternary system at 600 °C and 800 °C were studied for the first time using the diffusion couple technique and equilibrium alloy method with electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results reveal that the stable ternary intermetallic compounds were not found, while YCo2 and Co2Zr are formed a continuous solid solution phase (Y, Zr)Co2 with a Cu2Mg-type structure. The solid solubility of Zr in α-Y2Co17, YCo5, Y2Co7, α-YCo3, YCo and Y3Co at 800 °C was determined to be 5.6, 2.4, 9.4, 18.0, 1.4 and 1.4 at.%, respectively, while the solid solubility of Y in Co23Zr6, CoZr and CoZr3 was measured to be 6.4, 6.3 and 2.6 at.%. Meanwhile, the solid solubility of Zr in α-Y2Co17, YCo5, Y2Co7, α-YCo3, YCo, Y4Co3, Y3Co2, Y8Co5 and Y3Co at 600 °C was measured to be 4.4, 3.0, 9.4, 17.2, 1.6, 1.6, 1.9, 1.9 and 3.2 at.%, respectively, while the solid solubility of Y in Co23Zr6 and CoZr was measured to be 4.8 and 2.4 at.%. Two isothermal sections of the Y–Co–Zr ternary system at 600 °C and 800 °C were constructed finally. It provides the fundamental information for the development of high-performance Y–Co–Zr-based magnetic alloys.