Thermodynamic evaluation of Cu-Li phase diagram from EMF measurements and DTA study

Two experimental techniques were used in investigations of the Cu-Li system. An electrochemical concentration cell method was applied in measurements of activities of Li in Cu-Li alloys while DTA measurements were performed for liquidus and solidus determination. Activity measurements were Conducted using electrochemical cells with the liquid LiCl-LiF and LiCl-KCI electrolyte in the concentration range from X(Li) = 0.05-0.7 for 20 alloys and at temperatures between 633 K (360 degrees C) and 923 K (650 degrees C). DTA experiments were performed by derivatograph Q-1500 (Paulik-Paulik-Erdey system) for 17 alloys with concentration changing from X(Li) = 0. 18 to 0.975. The analyses of temperature dependencies of the electromotive force (EMF) for different concentrations of Cu-Li alloys indicated the existence of a new CU(2)Li(1) entropy-stabilized intermetallic phase. Using all available DTA literature data of Pastorello [S. Pastorello, Gazz. Chim. Ital. 60 (1930) 988-992] and Klemm and Volavesk [W. Klemm, B. Volavsek, Z. Anorg. Chern. 296 (1958) 184-187] and those from EMF and DTA measurements of this work the optimization and calculation of the Cu-Li system were performed. Finally, the thermodynamic properties of the fcc-(Cu), Cu(2)Li(3) intermetallic phase and the liquid phase were established together with a new proposed phase diagram of the Cu-Li system. The heat of formation of Cu(2)Li(3) compound established during the optimization of Cu-Li system is tentative and it should be experimentally confirmed or corrected in future investigations. (c) 2008 Elsevier Ltd. All rights reserved.