FATIGUE CRACK PROPAGATION IN A CAST MAGNESIUM ALLOY

Abstract— Fatigue crack propagation behaviour in a cast Mg-Al-Zn alloy was examined. The fatigue crack growth rate of the alloy under constant amplitude loading and the threshold resulting from a number of tests are given. Delayed retardation after the application of a single tension overload is explored in detail and described by using the model proposed by Matsuoka and Tanaka. From these observations, it may be seen that the Matsuoka model can be applied to the cast magnesium alloy as well as steels and aluminium alloys. Changes in the extent of retadation and the overload affected zone size with respect to the ratio of peak-to-baseline stress intensity factor range are discussed. Two phenomena, delayed arrest and acceleration in the later stages of retardation are reported.