Experimental investigation of phase equilibria and microstructure in the Co-Ti-V ternary system

The phase equilibria in the Co-Ti-V ternary system have been investigated by means of optical microscopy (OM), electron probe microanalyzer (EPMA), differential scanning calorimetry (DSC), field emission scanning electron microscope (SEM) and X-ray diffraction (XRD). The mechanical properties were measured by compressive tests. Four isothermal sections of the Co-Ti-V ternary system at 800 °C, 1000 °C, 1100 °C and 1200 °C were experimentally established. The results show that: (1) there is no ternary compound in this system; (2) the CoTi2 phase and Co3Ti phase stabilized by the V addition; (3) a large solubility of Ti in the σ-Co2V3 phase was observed at all isothermal sections of 800 °C, 1000 °C, 1100 °C and 1200 °C; (4) The alloy with the distribution of fine cuboidal Co3Ti (L12) in (αCo) phase was observed. (5) The compressive strength of Co77.29Ti5.83V16.88 (at.%) alloy at room temperature was measured to be about 1985 MPa. The newly determined phase equilibria in this system will provide useful information for the development of Co-based and Ti-based materials.