The aerospace field mainly develops high-strength, high-toughness and strong corrosion-resistant aluminum alloy materials to meet the harsh conditions of use in aerospace. The most widely used are 2xxx series aluminum and 7xxx series aluminum. Aluminum alloys for large aircraft structures are mainly 2xxx alloys( 2024, 2224, 2324, 2424, 2524,etc.) and 7xxx alloys( 7075, 7475, 7050, 7150, 7055, 7085, etc.), accounting for about 38% and 45% of the aluminum materials in civil airliners respectively.
The 2000 aluminum alloys mainly uses Cu as the main alloying element. The alloy prepared by adding an appropriate amount of Cu element to the aluminum alloy material will have a better improvement in strength, heat resistance, and processing performance, but the corrosion resistance will decrease, because the introduction of Cu element will make the interior of the aluminum alloy more prone to intergranular corrosion.
Therefore, for 2000-series aluminum alloys, pure aluminum or 6000-series aluminum alloys are generally coated on the surface as an electrochemical protective film for the bulk aluminum alloy to improve its corrosion resistance.
2024 aluminum alloy is an alloy that is frequently used in the aerospace industry. It is a high-strength alloy suitable for projects requiring a high strength-to-weight ratio and fatigue resistance. As such, it is primarily found in wing and fuselage structures that are often subjected to tension.
Al 2024 T6 is one main temper of 2024 aluminum. To achieve this temper, the metal is solution heat-treated and artificially aged until it meets standard mechanical property requirements. Its tensile strength is 61900 psi, yield strength is 50000 psi and elongation is 5%.
After anodizing treatment, the bending fatigue life of the 2014-T6 aluminum alloy under high stress is basically the same as that before treatment; under medium stress, the bending fatigue life of the material is greatly reduced; under low stress, the material has fatigue limit in 108 cyc.
As the thickness of the oxide layer on the surface increases, the bending fatigue resistance of the Al 2024 T6 material decreases. When the oxide layer increases to a certain thickness, the bending fatigue resistance of the material remains basically the same as the thickness of the oxide layer increases.
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