A thermodynamic modeling of the Pd–Ti system

The thermodynamic properties of the Pd–Ti system were optimized using the CALPHAD (CALculation of PHAse Diagram) technique. The solution phases, liquid, bcc, fcc and hcp, were described by the substitutional-solution model. Both compounds Pd2Ti and PdTi2 with tetragonal MoSi2-type structure were treated as one phase with the formula (Pd,Ti)2(Pd,Ti) by a two-sublattice model. The intermetallic compounds Pd3Ti, Pd3Ti2, and PdTi3 were treated as stoichiometric compounds. The intermetallic compound αPdTi, which had a homogeneity range, was treated as the formula (Pd,Ti)(Pd,Ti) by a two-sublattice model. A two-sublattice model (Pd,Ti)0.5(Pd,Ti)0.5 was applied to describe the compound βPdTi in order to cope with the order–disorder transition between βPdTi with CsCl-type structure (B2) and body-centered cubic solution (A2) in the Pd–Ti system. A set of self-consistent thermodynamic parameters was obtained.

► The Pd–Ti system was optimized using the CALPHAD technique.
► The order–disorder transition between βPdTi(B2) and bcc (A2) is described.
► A set of self-consistent thermodynamic parameters of the Pd–Ti system was obtained.