Effect of FSW parameters on residual stress, microstructure and mechanical performance of dissimilar 7075/2017A Al joints

Trdan, Uroš (author), Drev, Sandra (author), Klobčar, Damjan (author), Berlec, Tomaž (author), Ravnikar, Dunja (author)

This study investigates the effects of friction stir welding (FSW) parameters on residual stresses, microstructural evolution, hardness distribution, and tensile behaviour of dissimilar Al 7075-T651/Al 2017A-T451 joints. Three welding conditions with different welding ratios were analysed to clarify the role of heat input and material flow on joint performance. Residual stress measurements revealed asymmetric distributions typical of dissimilar FSW, with “M-shaped” longitudinal profiles and tensile stresses concentrated in the nugget zone. Lowest welding ratio (1.66 rev/mm) resulted in reduced tensile residual stresses and improved stress uniformity. Microstructural analyses showed sound weld formation with refined nugget-zone grains (∼2.5 – 3.5 μm), high-angle grain boundaries, and high dislocation density structures, indicating dynamic recrystallization dominated by severe plastic deformation. Thermally stable Al–Fe–Mn–Si-rich dispersoids persisted in the nugget zone, whose microstructure closely resembled that of the AA2017A base material, consistent with the dominance of the advancing-side alloy within the nugget zone. The optimal welding condition achieved the highest strength and ductility (Rp▫$_{0.2}$▫ = 304 ± 3 MPa, R▫$_{m}$▫ = 421 ± 2 MPa, A▫$_{t}$▫ = 8.4 ± 0.6%) and the 3-4 times lower weld-line heterogeneity Ψ compared to other conditions (e.g., Ψ–R▫$_{m}$▫: 0.98% vs. 3.47%), confirming enhanced mechanical uniformity. These results demonstrate that appropriate FSW parameter selection and precipitation stability are critical for producing structurally reliable dissimilar aluminium joints.

• Language: English
• Keywords: friction stir welding, FSW, high-strength dissimilar aluminium alloy, microstructure, microhardness, XRD residual stresses
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: Str. 5359-5373
• Numbering: Vol. 42
• PID: 20.500.12556/RUL-182195
• UDC: 621.791:669.715
• ISSN on article: 2238-7854
• DOI: 10.1016/j.jmrt.2026.04.136
• COBISS.SI-ID: 276723459
• Publication date in RUL: 29.04.2026

Record is a part of a journal

• Title: Journal of Materials Research and Technology
• Shortened title: J. Mater. Res. Technol.
• Publisher: Elsevier
• ISSN: 2238-7854
• COBISS.SI-ID: 519699737

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: varjenje z gnetenjem, FSW, aluminijeve zlitine, mikrostruktura, mikrotrdota, rentgenska difrakcija