High-Cycle Fatigue Behaviour of Ultrafine Grained 5052 Al Alloy Processed Through Cryo-Forging
Mechanical properties of ultrafine grained 5052 Al alloy processed through multi-directional forging were investigated in the present work. The as-received 5052 Al alloy was solution-treated (ST) at temperature 540 ℃ for two hours and subjected to multi axial forging at room temperature as well as liquid N2 temperature to a cumulative true strain of 4.2. The cryo-forged samples have exhibited a significant improvement in strength (380 MPa) and hardness (130 Hv) with 7.1% ductility, as compared to other conditions. Similarly, the high-cycle fatigue behaviour of the cryo-forged samples is found to be 80 MPa, which is better than other conditions. It was due to the formation of ultrafine grained microstructure with an average grain size of 230 nm in the cryo-forged samples. The formation of nanoshear bands in the cryo-forged samples, which accommodates the applied strain during cyclic loading is also responsible for dislocation accumulation along with broken/deformed impurity phase particles. The microstructure of the samples was characterized by optical microscopy, X-ray diffraction, and TEM to substantiate the mechanisms of grain refinement and its influence on the mechanical properties. Fractography of the tensile, as well as fatigue, tested samples were carried out using a Scanning Electron Microscope (SEM) to reveal the type of fracture.
KeywordsUltrafine grains Microstructure Characterization Fractography
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