Effect of Sb addition on the tensile deformation behavior of lead-free Sn–3.5Ag solder alloy

Tensile deformation behavior of Sn–3.5Ag and Sn–3.5Ag–1.5Sb alloys was investigated at temperatures ranging from 298 to 400 K, and strain rates ranging from 5 × 10⁻⁴ to 1 × 10⁻² s⁻¹. After melting and casting, the samples were rolled to sheets, from which tensile specimens were punched and pulled to fracture in uniaxial tension tests. Scanning electron microscopy (SEM) was used to study the microstructure and fracture surface of the samples. Addition of 1.5% Sb into the binary alloy resulted in an increase in both ultimate tensile strength (UTS) and ductility. The enhanced strength was attributed to the solid solution hardening effects of Sb in the Sn matrix. The improved ductility was, however, caused by the structural refinement which results in the higher strain rate hardening of the Sb-containing alloy. This was manifested by the higher strain rate sensitivity (SRS) indices (m) of 0.14–0.27, as compared to 0.11–0.20 found for the Sn–3.5Ag alloy.