Based first principle

the lattice constants

formation energy and demixing energy of Cu-Ni-Sn solid solution with different components were calculated.The results reveal that the Ni content has a great influence on the spinodal decomposition of Sn.When the Ni content is less than 20%

the demixing energy of Sn is increased with the increase of Ni content

and Cu-Ni-Sn solid solution with 20%Ni presents the strongest trend of spinodal decomposition.When the Ni content is more than 20%

the demixing energy of Sn is reduced sharply

and the solid solution with different Sn content can be formed stably and absence of spinodal decomposition occurrs.The spinodal decomposition trend of Ni is much stronger than that of Sn and little influenced by Sn content.The volume strain of the solid solution is decreased during the spinodal decomposition of Sn

while the volume of solid solution is increased during the spinodal decomposition of Ni.