Effect of Sb Addition on the Mechanical and Structural Behaviour of Sn-Bi alloy

Sn-12wt.% Bi (alloy A) and Sn-12wt.% Bi-1wt.%Sb (alloy B) solder
alloys homogenized at 463K for 24h were annealed for 2h at 443K. From both
alloys a group of samples was slowly cooled to room temperature with a
cooling rate of 1.2x10-2 K/s. A second group of samples was rapidly quenched
in cold water (273K). Stress-strain, σ−ε, tests performed in the temperature
range from (333-413) K in steps of 10 K, showed a temperature dependence of
the hardening behaviour with minimum at 353K followed by a peak at 363K
above which showed continuous decrease. The softening behaviour increased to
353K then showed minimum at 363K followed by continuous increase at higher
temperatures for both alloys. In the low temperature range the softening
coefficient, α, increased with Sb addition and its values were higher for the
slowly cooled samples than the quenched samples. The intrinsic hardness at
0K, Ho, was higher for the tertiary and quenched samples all over the tested
temperature range. In the high temperature range, α showed a constant value
of .02, Ho showed different values at 0K due to the different initial states of the
tested samples. Increasing the temperature and Sb addition lead to more
softening. The activation energy for the annealed and quenched samples of both
alloys were found to be 16.72 and 19.144 kJ/mol for the low and high
temperature regions, respectively. The average lattice parameters, “a”,
a
Δa , of
the Sn-rich phase showed two peaks at (343, 383)K and minima at 363k, while
“c”,
c
Δc and the ratio c/a decreased to minima at 353k and exhibited peaks at
(343, 363)k then decreased with further temperature increase.