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Estudo do comportamento mecânico da liga alumínio cobre 2024 solubilizada e envelhecida para aplicações aeronáuticas
Nilton Inácio Domingues Junior
DATA DE PUBLICAÇÃO
Aluminum alloys present low specific density, good strength, and high corrosion resistance under common environments. Aluminum-Copper 2024 alloy is one of the most widely used alloy in aircraft fuselage structures due to its good mechanical properties. The microstructure of the alloy was observed by optical microscopy showing elongated grains caused from the rolling process. Solution heat treatment was performed at 495, 505, and 515C followed by water quenching. Afterwards, artificial aging was carried out at 190 and 208C. Hardness measurements and tensile tests were performed to determine the mechanical properties of this material after heat treatments. Tensile and hardness tests exhibited similar mechanical properties for the alloy in the three solution temperatures (495, 505, and 515C). In general, the increase of the strength due to aging was accompanied by a decrease in ductility of the alloy. The highest values of yield and ultimate strength were obtained in the solubilized alloy at 505C and artificially aged at 208C/2h. A fatigue study on Al-2024 alloy was conducted under symmetric tension-compression at room temperature, using a rotating bending testing machine. S-N curve has not shown a typical fatigue limit, but a drop steadily with decreasing stress cycle. Specimen reached up to 7.8 x 106 cycles before fracture at 110.23 MPa. The fracture surfaces of specimens submitted to high stress and low number of cycles showed large quantity of precipitates and microvoids, while in specimens submitted to low stress and high number of cycles were observed the presence of cracks along the periphery of the fracture surface. The presence of pores was intercepted and pulled out of the matrix precipitates in the fracture surface during crack propagation of high cycle fatigue.