Effect of temper conditions on torsional behavior of selected 2000 series aluminum alloys at high strain rates
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In recent times, aluminum alloys have been widely used in different industrial sectors, including transportation, packaging, electrical, etc. Due to their lightweight and high specific strength and modulus, they are highly favored in the aerospace and automobile industries. Over the years, aluminum alloys have been produced in different grades (1000,2000, …, 8000) due to the high demand for newer alloys with better properties. This thesis focuses on deformation and damage mechanisms in AA2017, AA2024, and AA2624 aluminum alloys under high strain rate torsional loading. The mechanical response of the as-received aluminum alloys under high strain-rate torsional loading using torsional split Hopkinson bar was investigated. Cylindrical test specimens were subjected to high strain-rate torsional loading using angles of twist (ϕ) of 4°, 8° and 12°. Heat treatment processes were conducted on two sets of naturally aged specimens to obtain T651 and O temper condition. The effect of temper conditions on the microstructural evolution in the investigated alloys was investigated. Optical and scanning electron microscopy techniques were used to observe the morphology or composition of the second phase particles, grain structure, and crystallographic texture of the investigated alloys before and after rapid torsional deformation. Results from this study showed that the strength and ductility of the investigated alloys are dependent on the temper condition. Increasing the angle of twist resulted in the generation of higher strains and strain rates in the alloys for all temper conditions. Al-Cu-Mg alloys (AA2024, AA2624) have higher peak flow stress in the artificially aged condition than Al-Cu alloy (AA2017). The annealed specimens showed lower peak flow stress and higher ductility than their age-hardened counterparts. Artificial aging of AA2024 alloy led to lower plasticity and failure at lower stress levels than the naturally aged AA2024 alloy. In the naturally aged condition, AA2024 and AA2624 alloys exhibit the highest, and the lowest strength, respectively. Fractography of the AA2024-T651 specimen revealed a fracture mode that exhibits ductile features. Micrographs of the investigated alloys after torsional loading did not indicate heterogeneous deformation leading to strain localization and the development of adiabatic shear bands.
DegreeMaster of Science (M.Sc.)
CommitteeOguocha, Ikechukwuka N.; Cree, Duncan; Soliman, Haithem
Copyright DateJanuary 2022
angle of twist