Thermodynamic modeling of the Cr–Ni–Ti system using a four-sublattice model for ordered/disordered bcc phases

• The model of the NiTi phase in the Ni–Ti system is modified.
• The ΔfH of bcc ordering in the Ni–Ti system is computed by ab initio calculations.
• Four-sublattice model is used to describe the bcc ordered/disordered transition.
• An optimal set of thermodynamic parameters of the Cr–Ni–Ti system is obtained.

A thermodynamic assessment of the ternary Cr–Ni–Ti system together with a refinement for the thermodynamic description of the binary Ni–Ti sub-system is performed following the CALPHAD method and using the compound energy formalism (CEF). The ordered/disordered transition between disordered Bcc_A2 and ordered Bcc_B2 phases is described using a four-sublattice (4SL) model. An optimal set of thermodynamic parameters for the Cr–Ni–Ti system is obtained by considering the experimental data from the literature. Comparisons between the calculated and measured phase diagrams indicate that almost all of the reliable experimental information is satisfactorily accounted for by the present modeling. The complete liquidus projection and reaction scheme of the Cr–Ni–Ti system are also presented.