Comparative Studies of Microstructure and Fatigue Life of Selected Lead-free Alloys

Abstract

Lead-free alloys containing various amounts of zinc (4.5%, 9%, 13%) and constant copper addition (1%) were discussed. The results of microstructure examinations carried out by light microscopy (qualitative and quantitative) and by SEM were presented. In the light microscopy, a combinatorial method was used for the quantitative evaluation of microstructure. In general, this method is based on the phase quanta theory according to which every microstructure can be treated as an arrangement of phases/structural components in the matrix material. Based on this method, selected geometrical parameters of the alloy microstructure were determined. SEM examinations were based on chemical analyses carried out in microregions by EDS technique. The aim of the analyses was to identify the intermetallic phases/compounds occurring in the examined alloys. In fatigue testing, a modified low cycle fatigue test method (MLCF) was used. Its undeniable advantage is the fact that each time, using one sample only, several mechanical parameters can be estimated. As a result of structure examinations, the effect of alloying elements on the formation of intermetallic phases and compounds identified in the examined lead-free alloys was determined. In turn, the results of mechanical tests showed the effect of intermetallic phases identified in the examined alloys on their fatigue life. Some concepts and advantages of the use of the combinatorial and MLCF methods in materials research were also presented.

Archives of Foundry Engineering

“…The test was stress-controlled, increasing the stress value in subsequent groups of measurement cycles. Previous results obtained for SnZn9 [7], SnZn9Cu1 [8] alloys and for SnZn9Al1.5 alloy in this research show some differences in the influence of the third component in alloy on its deformability. Significantly lower deformability was found in the SnZn9Al1.5 alloy but it was obtained at a higher stress value.…”

“…It was also decided to compare present results with the results obtained previously for the binary SnZn9 [7] and SnZn9 alloy to which 1% of copper was added as a third component [8].…”

“…Conversely, in the case of the SnZn9Cu alloy, a much higher deformability was obtained with a lower stress value [8].…”

“…The results of tests carried out by the MLCF method are presented in Figures 7-9. The mechanical parameters UTS, R0.02, R0.2, Zgo, K' and Ra obtained for SnZn9Al1.5 alloy and also for SnZn9 [7] and SnZn9Cu1 [8] are shown in Figure 7. Fig.…”

“…7. Mechanical parameters: UTS, R0.02 (elastic limit), R0.2 (yield point), Zgo (assessed fatigue strength), K' (stress coefficient under cyclically varying loads) and Ra (accommodation limit) for SnZn9Al1.5, SnZn9 [7] and SnZn9Cu1 [8] alloys Modified low cycle fatigue test (MLCF) [10] based on Manson-Coffin-Morrow dependence:…”