Coupling modification of microstructure for improving the mechanical properties of Zn-Sn-Cu-Bi high-temperature solder

• Coupling modification has a great effect on improving the mechanical properties.
• The peritectic phase η was refined.
• Modification mechanism of ε phase was discussed.

In this study, an attempt to investigate a coupling modification method for grain refinement in Zn-Sn-Cu-Bi (ZSCB) high-temperature solder has been made. During coupling modification, primary grains nucleated from CeZn5 sites and grew to form much more ε-CuZn5 phases compared with the original solder. Peritectic η-Zn phases were also refined, transformed from matrix to equiaxed phases, with grain size of 1.40–2.24 µm and uniform elements distribution was achieved. By means of coupling modification, the mechanical properties of ZSCB high-temperature solder, the tensile strength and elongation, show indeed significantly improvement with an increase of 77.15% and 112.68%, respectively.

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