Density measurement of Sn-40Pb, Sn-57Bi, and Sn-9Zn by indirect Archimedean method

Abstract

By the indirect Archimedean method, the density and the density-temperature relationship of the Sn-40Pb eutectic alloy and two Pb-free solders, Sn-57Bi and Sn-9Zn eutectic alloys, were measured from room temperature to about 250°C. The results showed that the density-temperature dependence for each alloy in both solid and melting states can be fitted linearly as ρ_S(Sn-40Pb)=8.51−8.94×10⁻⁴(T−25°C), ρ_L(Sn-40Pb)=8.15−13.8×10⁻⁴(T−T_m); ρ_S(Sn-57Bi)=8.54−5.86 × 10⁻⁴(T−25°C), ρ_L(Sn-57Bi)=8.51−10.9×10⁻⁴(T−T_m); and ρ_s(Sn-9Zn)=7.22−7.78×10⁻⁴(T−25°C), ρ_L(Sn-9Zn)=6.89−5.88×10 ⁻⁴(T−T_m), where the density unit was g/cm³. At the melting point, density of the melt of these solders is 8.15 g/cm³, 8.51 g/cm³, and 6.89 g/cm³, respectively. The density decreased 2.6% for Sn-40Pb eutectic alloy during melting, and 2.7% for Sn-9Zn eutectic alloy, but increased 0.5% for Sn-57Bi eutectic alloy. The excess molar volume for these alloys after mixing at their melting point is 0.03 cm³/mol for Sn-40Pb, 0.09 cm³/mol for Sn-57Bi, and 0.21 cm³/mol for Sn-9Zn.