Microstructure and mechanical properties of Sn–58Bi eutectic alloy with Cu/P addition

Sn–(58-x) Bi–x Cu/P ternary alloys were prepared by downward continuous casting, and the microstructure of the alloy was characterized using scanning electron microscopy (SEM), x-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The results show that the addition of Cu and P can refine the eutectic structure and form rod-shaped Cu₆Sn₅ and P₃Sn₄ phases distributed in Sn matrix. The refined eutectic structure can be observed in Sn–(58-x) Bi–x Cu/P alloys, and this results in the elongation at break increases up. In addition, the wettability of Sn–58Bi alloy increases on Cu substrate with the addition of Cu and P elements. The improvement of the wettability of Sn–58Bi alloy by the addition of Cu element can be attributed to the increase of Cu-Sn IMC nucleation and growth rate. The addition of P element in Sn–58Bi alloy can improve its anti-oxidation performance, which is beneficial to the improvement of its wettability. (paper)