Effect of Zn addition, strain rate and deformation temperature on the tensile properties of Sn-3.3 wt.% Ag solder alloy

Stress-strain characteristics of the binary Sn-3.3 wt.% Ag and the tertiary Sn-3.3 wt.% Ag-1 wt.% Zn solder alloys were investigated at various strain rates (SR, ε .) from 2.6 x 10-4 to 1.0 x 10-2 s-1 and deformation temperatures from 300 to 373 K. Addition of 1 wt.% Zn to the binary alloy increased the yield stress σ y and the ultimate tensile stress σ UTS while a decrease of ductility (total elongation ε T) was observed. Increasing the strain rate (ε .) increased both σ y and σ UTS according to the power law σ = C ε .m. A normal decrease of ε T with strain rate was observed according to an empirical equation of the form ε T = A exp (- λε .); A and λ are constants. Increasing the deformation temperature decreased both σ y and σ UTS in both alloys, and decreased the total elongation ε T in the Zn-free binary alloy, whereas ε T was increased in the Zn-containing alloy. The activation energy was determined as 41 and 20 kJ mol-1 for these alloys, respectively. The results obtained were interpreted in terms of the variation of the internal microstructure in both alloys. The internal microstructural variations in the present study were evaluated by optical microscopy, electron microscopy and X-ray diffraction. The results show the importance of Zn addition in enhancing the mechanical strength of the Sn-3.3 wt.% Ag base alloy