Phase equilibria in Ti-rich portion and thermodynamic re-optimization of Co–Ti system
Hua-kou Yang1, Chen-yang Zhou1,2, Hang Wang1,2, Bin Yang1,2
1 Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi, China 2 Jiangxi Advanced Copper Industry Research Institute, Yingtan 335000, Jiangxi, China
Phase equilibria in Ti-rich portion and thermodynamic re-optimization of Co–Ti system
Hua-kou Yang1, Chen-yang Zhou1,2, Hang Wang1,2, Bin Yang1,2
1 Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi, China 2 Jiangxi Advanced Copper Industry Research Institute, Yingtan 335000, Jiangxi, China
摘要 The experimental and thermodynamic studies of the Co–Ti system are an important part of the project to build a thermodynamic database for multicomponent Co–Ti-based alloys. Several key alloys were prepared and then examined for microstructural, compositional and thermal analyses to determine the Ti-rich phase equilibria. According to the available experimental information, the Co–Ti system was thermodynamically re-optimized on the basis of CALPHAD method. Four disordered solutions, liquid, fcc-A1 (α-Co), bcc-A2 (β-Ti) and hcp-A3 (ε-Co and α-Ti) were modeled as substitutional ones. CoTi2 with limited solubility was treated as a stoichiometric compound, while γ-Co2Ti and β-Co2Ti with certain solubility were described in the form of (Co,Ti)2(Co,Ti)1 using a two-sublattice model. A single Gibbs energy function was employed to model two order–disorder transformations from fcc-A1 to fcc-L12 (Co3Ti) and from bcc-A2 to bcc-B2 (CoTi). A group of self-consistent thermodynamic parameters of the Co–Ti system were obtained. With these thermodynamic parameters, the experimental data can be described more reasonably and satisfactorily.
Abstract：The experimental and thermodynamic studies of the Co–Ti system are an important part of the project to build a thermodynamic database for multicomponent Co–Ti-based alloys. Several key alloys were prepared and then examined for microstructural, compositional and thermal analyses to determine the Ti-rich phase equilibria. According to the available experimental information, the Co–Ti system was thermodynamically re-optimized on the basis of CALPHAD method. Four disordered solutions, liquid, fcc-A1 (α-Co), bcc-A2 (β-Ti) and hcp-A3 (ε-Co and α-Ti) were modeled as substitutional ones. CoTi2 with limited solubility was treated as a stoichiometric compound, while γ-Co2Ti and β-Co2Ti with certain solubility were described in the form of (Co,Ti)2(Co,Ti)1 using a two-sublattice model. A single Gibbs energy function was employed to model two order–disorder transformations from fcc-A1 to fcc-L12 (Co3Ti) and from bcc-A2 to bcc-B2 (CoTi). A group of self-consistent thermodynamic parameters of the Co–Ti system were obtained. With these thermodynamic parameters, the experimental data can be described more reasonably and satisfactorily.
Hua-kou Yang,Chen-yang Zhou,Hang Wang, et al. Phase equilibria in Ti-rich portion and thermodynamic re-optimization of Co–Ti system[J]. Journal of Iron and Steel Research International, 2022, 29(6): 914-924.
2022, Vol. 29 
