Investigation of phase equilibria in the Ti-Co-Zr ternary system

Abstract Isothermal sections of the Ti-Co-Zr ternary system at 1073 K and 1173 K were determined using Ti-Co-Zr diffusion triples and equilibrated alloys with optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and electron probe micro-analysis (EPMA) techniques. A unknown ternary phase with composition of ～Ti 31.3 Co 37.9 Zr 30.8 was observed to be stable at both 1073 K and 1173 K. Two continuous solid solutions Co 2 (Ti, Zr) and Co(Ti, Zr) were formed between the binary intermediate compounds Co 2 Ti (c) and Co 2 Zr (c) as well as between the CoTi and CoZr intermediate compounds, respectively. The solubility of Zr in the CoTi 2 phase was nearly 55.0 at% at both 1073 K and 1173 K, and the Co 11 Zr 2 phase was proved to be non-existent at 1073 K and 1173 K. Liquid phase was observed at 1173 K and exists with a wide range in the Ti-Zr-rich part.