Identification and characterization of ß→α-Sn transition in SnCu1 bulk alloy inoculated with InSb

Abstract

In this paper, the allotropic transition of s to α-Sn (so called “tin pest”) was identified with electrical resistance measurements. Samples were prepared from SnCu1 alloy using mechanical treatment of two different sample sizes, artificially inoculated with InSb and stored at −18°C for 9 weeks. The electrical resistance measurement showed that in the case of SnCu1 solder alloy the α-Sn transition has three stages: nucleation, growth and the saturation phase, when the transition is almost stopped. It was proven by focused ion beam cross-sectioning and Mosbauer spectroscopy that the developed α-Sn phase can enclose the metastable non-transitioned s-Sn preventing its further transition and resulting the saturation phase of the phenomenon. In addition, the results point out that the rate of vertical expansion of the α-Sn into the sample body can be equivalent or higher than the horizontal expansion.