Thermodynamic modelling of the Co-Ti system

In the Co-Ti system many solid solutions are present: A1, L1(2), A2, B2, A3, and Laves C15 and C36 phases. Two of them exhibit order/disorder transitions: Al and L12, A2 and B2. In this optimisation the sublattice model has been used to describe the ther modynamic functions of the above-mentioned phases. The order/disorder transformation A1 <--> L1(2) has been described by modelling the L1(2) phase with either two or four sublattices both descriptions being mathematically equivalent. The A2 <-->B2 relation was also modelled in a similar way. The cited solid solutions, together with the liquid (Redlich-Kister excess model) and the CoTi2, considered as stoichiometric, phases have been optimised by means of the Thermo-Gale software, on the basis of the literature data concerning both phase equilibria and thermodynamics. (C) 2000 Elsevier Science Ltd. All rights reserved.