Effect of small addition of zinc on creep behavior of tin

Abstract

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-0.4mass%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-0.4mass%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. © 2010 The Japan Institute of Metals.