FATIGUE CRACK GROWTH BEHAVIOR OF HOT ROLLED AA2050-T84 PLATES

Date

2023-9-11

Author

Ata Tufan, Begüm

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Lithium-containing aluminum alloys have gained prominence in aerospace applications due to their lower density and improved elastic modulus compared to other aluminum alloys. Aluminum-lithium alloys have been developed to address weight and performance requirements in future aircraft. Among the third-generation aluminum-lithium alloys, AA2050 has emerged as a potential replacement for incumbent plate alloys, such as 7xxx and 2xxx alloys, offering high strength, fatigue crack growth resistance, and damage tolerance while enabling weight savings. This study focuses on comprehensively characterizing the microstructure and mechanical properties of AA2050-T84 alloy. Two hot rolled plates having 20 mm and 130 mm thickness were used in this study. The plates underwent identical production stages except for the extent of hot rolling, which was higher for the 20 mm thick plate. A comparative analysis between the two plates aims to understand how the grain anisotropy and orientation affect the overall mechanical performance of the alloy. Moreover, fatigue tests and fatigue crack growth tests are conducted to assess the resistance of the alloy to cyclic loading-induced damage. Importantly, the highly anisotropic grain structure and the preferred crystallographic orientation in the 20 mm thick plate were found to cause a fatigue crack deviation. Fractographic analyses of the 20 mm thick plate (when the loading was parallel to the rolling direction) exhibited microcrack formations perpendicular to the crack growth direction and slip bands at the intermediate ΔK. Collectively, the findings from this study contribute to the existing knowledge of AA2050 alloy properties and offer critical insights into how the rolling operation for achieving thin plates influences the microstructure and overall performance of the alloy.

Subject Keywords

AA2050-T84, Fatigue Crack Growth, Fracture, Crack Deviation, Microstructure

URI

https://hdl.handle.net/11511/105408

Collections

Graduate School of Natural and Applied Sciences, Thesis