The effects of antimony additions on microstructures, thermal and mechanical properties of Sn-8Zn-3Bi alloys

In this paper, the effect Sb on the microstructure, thermal and mechanical properties of Sn-8Zn-3Bi alloys was studied. With addition of 0.5–1.5 wt.% Sb, melting temperature and undercooling is slightly increased compared with Sn-8Zn-3Bi alloy, while the pasty range remains unchanged. It was found that the addition of Sb refined the microstructure, resulting in a smaller α-Zn phase, and enlarged the Sn-Zn eutectic area, without intermetallic compound (IMC) formation. Mechanical properties are significantly improved by micro-alloying and this is attributed to solid solution strengthening. With the addition of 1.5 wt.% Sb, tensile strength, yield stress and Young's modulus was improved by 14.5%, 87% and 116.2% respectively, compared with the Sn-8Zn-3Bi solder alloy. Elongation was increased by 28%, due to a more ductile fracture mechanism. The relatively low melting temperature, superior mechanical properties, along with narrow pasty range and undercooling, makes Sn-8Zn-3Bi-xSb alloy system a potential low temperature lead-free alloy for temperature sensitive applications such as optoelectronics, crystal oscillators, MEMS devices, and internet-of-things (IoT) devices.