Effects of lanthanum on microstructure and solidification mechanism of (Ag-Cu ₂₈)-25Sn-xLa alloys

Effects of La addition on the microstructure and solidification process of (Ag-Cu ₂₈)-25Sn alloys were simultaneously studied. After high frequency induction heating, the (Ag-Cu ₂₈)-25Sn-xLa alloys were prepared by water quenching. The phase compositions, solidification microstructures and distribution of elements of (Ag-Cu ₂₈)-25Sn alloys were analyzed by XRD, SEM and EDS. The result showed that rare earth La was added, the phase compositions of (Ag-Cu ₂₈)-25Sn alloy could be changed. When the addition of La was less than 0.5%(mass fraction), the phase compositions of (Ag-Cu ₂₈)-25Sn alloys were Ag ₃Sn, Cu ₃Sn and Cu ₆Sn ₅. When the addition of La was more than 1.0%, the phase compositions of (Ag-Cu ₂₈)-25Sn alloys were Ag ₃Sn and Cu ₃Sn. Meanwhile, the primary phase of Ag(Sn) solid solution could be easily dissolved out, and the solidification structures of that could be refined.