Effect of Small Addition of Zinc on Creep Behavior of Tin

Sn-based alloys with high creep resistance are required for soldering applications. This paper describes the effect of solid solution strengthening on the creep resistance of Sn-Zn alloys. The maximum solubility limit of Zn is 0.34 mass% in Sn. The creep behaviors of Sn, Sn0.1 mass%Zn and Sn-0.4 mass%Zn were examined at 298 and 398 K under constant strain rates ranging from 1 � 10 � 4 to 1 � 10 � 2 s � 1 . The creep resistance of Sn was improved significantly by the addition of a small amount of Zn owing to the solid solution strengthening. The creep resistance of Sn-0.4 mass%Zn was at the same level as that of Sn-37 mass%Pb. We obtained a stress exponent of about 7 and an activation energy of 41–45 kJ/mol, which indicates that the creep behavior was climb-controlled dislocation creep controlled by pipe diffusion. The finding that a small addition of Zn improves the creep resistance is useful for developing new Pb-free solders. [doi:10.2320/matertrans.MJ201023]