2xxx Al-Cu-Mg can be heat-treated and strengthened processed aluminum alloy. It main alloying elements are copper and magnesium, and also contain a small amount of manganese, chromium, and other elements. The copper content of the aluminum-copper alloy is 2% to 10%, and the alloy containing 4% to 6% Cu has the highest strength. Its distinctive feature is high hardness even at high temperature.
2024 aluminum is an Al-Cu-Mg aluminum alloy. It has a density of 2.73 g/cm3. It can be strengthened by heat treatment and has moderate plasticity in the quenched and just-quenched state. 2024 aluminum plates are mainly used to make various long-term load parts and prefabricated components (but not including metal stamping parts and steel castings) such as aircraft frame parts, skins, bulkheads, ribs, spars, bolts.
The common tempers of 2024 aluminum sheet are O temper, T3/T351 and T4 temper.
O temper | Annealing |
T3/T351 temper | Solution heat treatment + cold working + natural aging (Stretch to relieve stress) |
T4 temper | Solution heat treatment + natural aging |
Alloy Al 2024 t3 is one of the most widely used alloys in airframe construction. It has moderate yield strength, good resistance to fatigue crack growth and good fracture toughness. The 2024 aluminum alloy remains an important aircraft structural material due to its excellent damage tolerance and high resistance to fatigue crack growth under the T3 aging condition.
2024 t4 aluminum has the lowest sensitivity to intergranular corrosion. The aging temperature is 190 ℃ and the holding time is 9h.
For different tempers, they all can be corroded. Among them, the intergranular corrosion is very obvious in the three states of aging at 150 ℃ for 16 hours, 230 ℃ for 9 hours and annealing. The intergranular corrosion at 150 ℃ for 16 h is the most serious, indicating that this aging process reduces the corrosion resistance of aluminum alloy while increasing the mechanical properties of the material.
When the aging temperature is 190 ℃, the degree of intergranular corrosion of the sample kept for 16 h is greater than that of 9 h; when the aging temperature is 230 ℃, the degree of intergranular corrosion of the sample kept for 9 h is greater than that of 16 h.
In addition, from the microstructure photos of intergranular corrosion, 2024 t4 aluminum (493 ± 2℃ solution treatment + natural aging) is more resistant to intergranular corrosion, therefore solution treatment plus natural aging to a stable state is the best heat treatment system for 2024 aluminum alloy.
This is directly related to the more dispersed and uniform distribution of the second phase CuAl2 under the natural aging system. Because the natural aging reduces the electrochemical difference of the grain boundary to a great extent, thereby improving the intergranular corrosion resistance under the natural aging system.
Original Source:https://www.aircraftaluminium.com/a/aviation-aluminum-alloy-2024t3-t4.html
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