Compositional partitioning during the spinodal decomposition in Cu-Ni-Sn alloy.

Spinodal decomposition in Cu-9.4at%Ni-3.1at%Sn alloy was elucidated with the new insight from the experimental EXAFS analysis supported by <italic>ab initio</italic> total energy calculations suggesting the strong influence of the first near-neighbour atoms. Enthalpy of mixing was calculated for all crystallographically unique first near-neighbour configurations and finally an average positive enthalpy of mixing of 1604 J/mol was obtained. Combination of <italic>ab initio</italic> results, XRD and EXAFS analysis indicate that one of the daughter phase becomes rich in Ni and Sn than the other phase; in contrary to the earlier proposition that Cu/Ni ratio remains constant in both daughter phases. It is also shown that the present thermodynamic description requires further refinement to extend the miscibility gap towards lower Ni content in Cu-Ni-Sn system. [ABSTRACT FROM AUTHOR]