Fracture toughness and fatigue crack propagation rate in 2024 alloys have been investigated through changing the morphologies of constituens and dispersoids. Fracture toughness is proportional to the square root of the spacing of constituents, mainly Cu
2FeAl
7 in 2024 alloys. Broadening the spacing from 58μm to 140μm, the fracture toughness increases by 18%. The fact that the dimple diameter becomes larger with increasing constituent spacing leads to the increase in fracture toughness. In a low Δ
K region, the fatigue crack propagation rate becomes slower mainly by broadening the spacing of dispersoids, Cu
2Mn
3Al
20. Broadening the spacing from 0.45μm to 0.64μm, the propagation rate decreases by 50%. In a high Δ
K region, on the other hand, the propagation rate becomes slower mainly by broadening the spacing of constituents.
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