Thermodynamic assessment of the Cu–Li system and prediction of enthalpy of mixing of Cu–Li–Sn liquid alloys

After a comprehensive review of the thermochemical and phase diagram data in the Cu-Li system, new experiments were performed to clarify existing contradictions. Several Cu-Li samples were prepared and powder X-ray diffraction (XRD) was performed on quenched Cu-Li alloys. Our experimental work could not confirm the presence of the intermetallic phase Cu ₂Li ₃ which has been recently proposed. Additionally, the results of our high temperature enthalpy of mixing measurements of the liquid phase indicate that the Li-rich liquidus line is more Cu-rich than presented in previous works. Based on our experimental data, a Calphad approach was used to obtain a self-consistent thermodynamic description of the Cu-Li binary system. Furthermore, a preliminary description of the ternary Cu-Li-Sn liquid phase was developed by combining the new description of the liquid phase in the Cu-Li system with the description of the liquid phase from our previous Cu-Sn and Li-Sn assessments. The enthalpies of mixing of the liquid phase calculated using extrapolations according to the associate, Muggianu, and Toop models are compared to the enthalpies of mixing reported in the literature. Our work shows that the enthalpies of mixing calculated using the associate model are in excellent agreement with the literature data, and no additional ternary interaction parameters are necessary. The contribution of the formation of Li ₄Sn associates to the enthalpy of mixing of the ternary liquid was discussed.