Initiation and propagation behavior of fatigue crack in 2524-T34 alloy

The fatigue performance of 2524-T34 sheets was studied by four-point bend fatigue test. The fatigue crack initiation and propagation behavior were observed by optical microscopy and scanning electron microscopy. The results indicate that 2524 alloy shows superior fatigue properties. The fatigue strength is up to 80% of the yield strength. The fatigue crack mainly initiates from the second phase particles and the interface between the second phase particles and matrix. The crack plane deflection in the process of crack propagation relates to the resistance of the grain boundary. The difference of crystallographic orientation between the two favoured slip planes within the two neighboring grains is an important factor to control crack propagation across a grain boundary.