| The thermomechanical fatigue properties of 96.5 wt.% Pb 3.5 wt% Sn alloy were studied at temperatures ranging from 15;Strong thermomechanical and phase effects were seen. The number of cycles to failure was seen to be smaller, when the peak temperature of the temperature cycle coincided with the peak tensile strain, than in an isothermal test under the same conditions except at the peak temperature of the thermal cycle. The number of cycles to failure was larger, when the lowest temperature of the thermal cycle coincided with the peak tensile strain, than in an isothermal test under the same conditions except at the maximum temperature of the thermal cycle and, where measured, at the minimum temperature of the thermal cycle as well. Also, unusual dependence of the number of cycles to failure on frequency was observed.;These and other results were modeled using a vacancy-impurity complex model. Oxygen was chosen as the principal impurity since fatigue tests were conducted in air. Treating the complexes thermodynamically as if they were a chemical compound, the theoretical dependence of the number of cycles to failure on oxygen partial pressure was explored. |
