Effects of secondary particle-induced recrystallization on fatigue crack growth in AA2524/AlCuMg T3 alloy sheets

The effects of secondary particle-induced local recrystallization on fatigue crack growth in electromagnetically cast AA2524/AlCuMg T3 alloy sheets were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and fatigue tests. A neck-lace-like structural model, which was composed of coarse secondary particles and fine grains, was established to describe the observations. The results showed that the fatigue crack growth rate was significantly lowered by the pronounced secondary particle-induced local recrystallization, owing to the resulting stress concentration and the microstructural scale effect. The sheets with a more dispersed distribution of the secondary particles, which corresponded to a larger inter-particle spacing, exhibited the highest fatigue crack growth resistance in the stable stage of crack extension.