Effect of strain rate and temperature on micro fatigue crack propagation of Bi-Sn eutectic alloy

Effects of strain rate and temperature on fatigue crack growth of Bi-Sn eutectic alloy were investigated. The micro fatigue crack propagation rate decreases with a decrease in strain rate and an increase in temperature when compared with in the same strain range. This is an opposite trend to the effect of strain rate and temperature observed in common high temperature fatigue fractures. The result is attributed that fatigue crack propagation does not increase even by strain reduction and temperature increase, since cavity formation is suppressed by viscous deformations of grain interior. Fatigue crack propagation rate is controlled only by strain energy which is the driving force for crack propagation. As a result, the rate of crack propagation and the number of crack initiation cycles can be assessed by ΔJ, not by strain rate and temperature.