New aspects of development of high strength aluminum alloys for aerospace applications

New aspect of developing the materials in lights of interrelationship among alloy/process microstructure (mainly the second phase particles) - properties combined with micromechanics has been carried out in 2024 aluminum alloys. The fracture toughness is proportional to the square root of the spacing of constituents, Cu2FeAl7, in 2024 aluminum alloys. Broadening the spacing 75-140 mu m, the fracture toughness increases by 20%. In a low Delta K region, the fatigue cracks propagate much slowly by broadening the spacing of dispersoids, Cu2Mn3Al20. Broadening the spacing, the crack propagation rate decreases by 50%. The larger size of dispersoids, Cu2Mn3Al20, makes the rate much slower than smaller ones, Cr2Mg3Al18 or ZrAl3. On the other hand, in a high Delta K region, the rate becomes slower mainly by broadening the constituents spacing. The newly developed 2 x 24 aluminum alloy sheets, in these concepts in mind, have excellent fracture toughness and fatigue crack propagation characteristics to provide lower weight, higher damage tolerance, and longer-term durability for aerospace applications. (C) 2000 Elsevier Science S.A. All rights reserved.