The study includes the results of research conducted on selected lead-free binary solder alloys designed for operation at high temperatures.
The results of qualitative and quantitative metallographic examinations of SnZn alloys with various Zn content are presented. The
quantitative microstructure analysis was carried out using a combinatorial method based on phase quanta theory, per which any
microstructure can be treated as an array of elements disposed in the matrix material. Fatigue tests were also performed using the
capabilities of a modified version of the LCF method hereinafter referred to in short as MLCF, which is particularly useful in the
estimation of mechanical parameters when there are difficulties in obtaining many samples normally required for the LCF test. The fatigue
life of alloys was analyzed in the context of their microstructure. It has been shown that the mechanical properties are improved with the
Zn content increasing in the alloy. However, the best properties were obtained in the alloy with a chemical composition close to the
eutectic system, when the Zn-rich precipitates showed the most preferred morphological characteristics. At higher content of Zn, a strong
structural notch was formed in the alloy because of the formation in the microstructure of a large amount of the needle-like Zn-rich
precipitates deteriorating the mechanical characteristics. Thus, the results obtained during previous own studies, which in the field of
mechanical testing were based on static tensile test only, have been confirmed. It is interesting to note that during fatigue testing, both
significant strengthening and weakening of the examined material can be expected. The results of fatigue tests performed on SnZn alloys
have proved that in this case the material was softened.