Thermodynamic re-assessment of Fe-Ti binary system
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Laboratory for Joining and Interface Technology, Swiss Federal Laboratories for
Materials Science and Technology, Überlandstrasse 129, CH-8600, Dübendorf, Switzerland;
3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China)
2. Laboratory for Joining and Interface Technology, Swiss Federal Laboratories for
Materials Science and Technology, Überlandstrasse 129, CH-8600, Dübendorf, Switzerland;
3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China)
Abstract: The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.
Key words: Fe-Ti system; order-disorder transition; thermodynamic assessment; phase diagram; CALPHAD