Phase equilibria of the Co–Mo–Ti system at 950°C

Abstract: The phase equilibria at 950°C of the Co–Mo–Ti system was investigated by a combination of a diffusion couple technique and equilibrated alloys. The samples were examined by means of optical microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction analysis. The isothermal section of the Co–Mo–Ti system at 950°C consists of 7 three-phase fields and 15 two-phase fields. The following five three-phase equilibria were well determined: (1) TiCo2 (h)+MoCo3 +Mo6Co7, (2) TiCo2 (c)+TiCo2 (h)+TiCo, (3) TiCo2 (h)+TiCo+Mo6Co7, (4) TiCo+Ti2Co+(Mo,Ti), and (5) TiCo+Mo6Co7 +(Mo,Ti). The solubility of Ti in Mo6Co7 was determined to be 23.1at.% Ti. The solubilities of Mo in TiCo2 (h), TiCo2 (c), and TiCo were measured to be 11.4, 4.7, and 5.4at.% Mo, respectively. The solubility of Mo in Ti2Co is about 0.3at.% Mo. The two-phase region of TiCo3 +MoCo3 was found to be very narrow and close to the TiCo3 side. [Copyright &y& Elsevier]