Effect of constituents and dispersoids morphology on fracture toughness and fatigue crack propagation rate in 2024 aluminum alloys

Fracture toughness and fatigue crack propagation rate in 2024 alloys were investigated by changing constituents and dispersoids morphology. Fracture toughness is proportional to the square root of the constituents(mainly Cu2FeAl7) spacing. If the spacing is widened from 75 mu m to 142 mu m, the fracture toughness increases by 20%. The fact that the dimple diameter becomes larger with increasing constituents spacing leads to the increase in fracture toughness. At a low Delta K level, the fatigue crack propagation rate becomes lower, mainly by widening the spacing of dispersoids, Cu2Mn3Al20. If the spacing is widened from 0.53 mu m to 0.70 mu m, the propagation rate decreases by 50%. At a high Delta K level, on the other hand, the propagation rate becomes lower, mainly by widening the spacing of constituents.