Thermodynamic modelling of the Ti–Sn system and calculation of the Co–Ti–Sn system

The phase transformation temperatures of the Ti-Sn system at Sn-rich portion are determined by DTA. The optimized descriptions of the phase diagram and thermodynamic properties of the Ti-Sn system have been obtained from experimental data by means of the CALPHAD technique. The system contains five intermetallic compounds from which Ti5Sn3, Ti6Sn5 and Ti2Sn3 are stoichiometric compounds. The sublattice models of (Sn, Va) (Ti,V a)2 and (Sn, Va) (Ti)3 have been used to describe the homogeneity ranges of Ti2Sn and Ti3Sn, respectively. A consistent set of thermodynamic parameters for each phase is derived. Optimized results and most of the experimental data are in good agreement. For the Co-Ti-Sn ternary system, sublattice model (Co, Va)(Co)(Ti)(Sn) is proposed to describe the homogeneity range of ternary compound Co2SnTi. Based on the literature data of thermodynamic assessment of Co-Sn and Co-Ti and the present work of Ti-Sn system, the phase diagram calculation of Co-Ti-Sn is carried out. Results show that more experiments about the phase relations of the Co-Ti-Sn ternary system are necessary.