Microstructure and texture evolution of friction stir lap welded dissimilar multi-aluminum stack

Journal Article · 17 October 2023 · Materials Characterization

DOI: https://doi.org/10.1016/j.matchar.2023.113398 · OSTI ID:2341758

Das, Hrishikesh ^[1]; Kalsar, Rajib ^[1]; Shukla, Shivakant ^[1]; Anaman, Sam Y. ^[2]; Upadhyay, Piyush ^[1]; Cho, Hoon-Hwe ^[2]

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1. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Applied Materials & Manufacturing Group
2. Hanbat National University (South Korea)

Here this work investigates the microstructural evolution of a dissimilar multiple-aluminum alloy stack (AA7055, AA7055, AA6022) produced by friction stir lap welding (FSLW). A through-thickness analyses of grain orientation map, grain size and distribution, strain distribution, and texture evolution by electron backscattered diffraction-based characterization technique were performed. Two different welding parameters (combination of tool rotation and traverse speed) were used to study the effects of the welding parameters on these microstructural characteristics. The study shows that higher welding speed and higher rotation speed of the FSLW tool yield finer grains. FSLW resulted in shear texture formation in the weld regions due to high welding speeds. This texture development in the nugget zone is consistent with shear deformation, and (111) pole figures show ideal shear texture components. The Stir Zone (SZ) exhibits shear texture (A/A ̅ and B/B ̅ components), consistent with other shear-assisted processes. Recrystallization mechanisms observed are CDRX in SZ and DDRX in TMAZ (Thermo-Mechanically Affected Zone). Interface analysis reveals the presence of oxide layers between different aluminum sheets, affecting joint mechanical performance. The mechanical property of the lap welded joints was presented in terms of microhardness distribution across the weld cross section. Slightly higher hardness in higher speed welding setup was observed throughout the SZ and AA6022 layer, indicating greater grain refinement and uniform grain structure distribution.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO); National Research Foundation of Korea (NRF)
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 2341758
• Report Number(s): PNNL-SA--184435
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Journal Issue: Part A Vol. 206; ISSN 1044-5803
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English