Effect of annealing and microstructure on the creep behaviour of an Sn-10 wt % Sb alloy

This paper concerns the effect of the two-phase microstructure (solid solution plus SnSb intermetallic) on the creep behaviour of an Sn-10 wt % Sb alloy. The alloy was specially cast and drawn into wires of 0.55 mm diameter. Samples were heat treated at temperatures of 348, 373, 398, 423 and 448 K to produce a range of volume fractions of the intermetallic ß-phase SnSb. Constant-load creep tests were carried out at room temperature for each of the wire samples. The results obtained show that there is a relationship between the heat-treatment temperature T_a and the microstructure and that this, in turn, affects the creep properties of the alloy. Quantitative scanning electron microscopy (SEM) analysis has been used to determine the relationship between the microstructure and the mechanical behaviour of the alloy independently of any microstructural changes which might occur during creep at more elevated temperatures. It is shown that the steady state creep rate can be described in terms of the mass fraction X_Sb of antimony dissolved in the matrix phase, the mean grain size d (µm) and the applied stress s (MPa) by the equation e? = 3.75 × 10^-17 X_Sb^-1 d^-0.59 s^8.19, where the strain rate is given in reciprocal seconds. Comparisons are made with other observations on the creep resistance of solder alternatives. © IMechE 1999.