EAPSI: Understanding the Effects of High Pressure and Heat on an Aluminum Alloy

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Aluminum 2139 is a copper-based aluminum (Al) alloy that is used in the aerospace industry and has an attractive mixture of strength and toughness. Traditional welding methods cause copper containing Al alloys to crack, which is unacceptable for structural components. However, this can be circumvented by melting the joined area of two plates clamped together and using a rotating tool to stir this softened area until the softened area from both plates have mixed. This is called friction stir welding. Research conducted at Michigan State University (MSU) has demonstrated that the welded region is weaker than the unwelded base metal region. In an effort to improve its performance, the friction stir welded region will undergo post-weld heat treatment (PWHT). The unwelded region will undergo high pressure torsion (HPT) to investigate how high pressure processing affects the performance of this alloy. This work will be performed in collaboration with Professor Mitsuo Niinomi at the Institute for Materials Research (IMR) at Tohoku University in Japan. The IMR personnel have notable expertise in HPT as well as related data characterization and analysis.The total material strain, the microstructural phases present and their volume fraction, microstructure and dislocation structures, and hardness of the HPT treated samples will be characterized in this study using EBSD, x-ray diffraction, transmission electron microscopy imaging, and Vickers hardness testing. Mechanical tensile testing will be performed. The PWHT experiments will be grouped as: solution treatment, solution treated and artificially aged, and artificially aged. These samples will then be polished and characterized at Tohoku University using EBSD, x-ray diffraction, and Vickers hardness testing. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.