Experimental determination of phase equilibria in the Ce–Co–Ti ternary system

Abstract The phase equilibria of the Ce–Co–Ti ternary system at 873 K and 1,073 K were determined for the first time by using the equilibrium alloy method in combination with scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction. The ternary intermetallic compound CeCo 12- x Ti x with a ThMn 12 -type structure was detected to exist at 873 K and 1,073 K. The composition range of CeCo 12- x Ti x was measured to 7.8–14.6 at.% Ti at 873 K and 8.4–14.8 at.% Ti at 1,073 K, respectively. Due to the partial substitution of Co by Ti, the metastable binary intermetallic compound CeCo 7 with a TbCu 7 -type structure was confirmed to be stable at 873 K, and the solid solubility of Ti in CeCo 7 was determined to be 3.3 at.%. The experimental results show that the maximum solid solubility of Ti in Ce 2 Co 17 (rt), CeCo 5 , Ce 5 Co 19 , Ce 2 Co 7 (ht), CeCo 3 , and CeCo 2 at 873 K is 6.0 at.%, 1.4 at.%, 1.3 at.%, 4.1 at.%, 1.2 at.% and 2.2 at.%, respectively, while the composition ranges of Co 3 Ti, Co 2 Ti(c), and CoTi are 75.2–82.0 at.% Co, 66.0–67.5 at.% Co and 48.5–53.8 at.% Co. Meanwhile, the maximum solid solubility of Ti in Ce 2 Co 17 (rt), CeCo 5 , Ce 5 Co 19 , Ce 2 Co 7 (ht), CeCo 3 , and CeCo 2 at 1,073 K was measured to be 5.3 at.%, 2.8 at.%, 0.5 at.%, 2.8 at.%, 0.9 at.%, and 2.5 at.%, respectively, while the composition ranges of Co 3 Ti, Co 2 Ti(c), and CoTi are 74–79.7 at.% Co, 65.6–68.5 at.% Co and 51.4–53.5 at.% Co. Finally, two isothermal sections of the Ce–Co–Ti ternary system at 873 K and 1,073 K were established.