Abstract
ABSTRACT The Sn-9Zn eutectic alloy has been considered as a potential replacement for toxic lead-based solders for its lower melting point (198 °C) and improved mechanical properties compared to traditional lead-based solder alloys. This paper investigates the influence of bismuth (Bi) addition as a surface-active element on the structural, thermal, mechanical, and electrical properties of eutectic Sn–9Zn alloy. Different amounts of Bi were added (x = 0.5, 1, 2, 3, wt %) to study the characteristics of Sn-9Zn-xBi ternary alloys followed by annealing at 150 °C for 60 minutes. Microstructures and phase constituents of developed alloys were examined and compared using optical microscopy and XRD respectively. The melting point and coefficient of linear thermal expansion were determined by differential thermal analysis and thermo-mechanical analysis. Tensile Properties (ultimate tensile strength, elongation, %), microhardness (HV), and electrical conductivity (% IACS) were measured. The results indicated that the addition of Bi decreased the melting point by about 10 °C, the heat of fusion, coefficient of thermal expansion, electrical conductivity than Sn-9Zn eutectic alloy. Bi addition enhanced the ultimate tensile strength and hardness by about 65% by 50% respectively. SnBi inter-metallic compound (IMC) precipitates were formed and extracted from the β-Sn matrix with a non-uniform microstructure.
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