Modified friction stir clinching of 2024-T3 to 6061-T6 aluminium alloy: Effect of dwell time and precipitation-hardening heat treatment

This paper investigates the effect of dwell time and heat treatment on the modified friction stir clinched (MFSC) joint of AA2024-T3/AA6061-T6 Al alloys. The precipitation-hardening heat treatment method involves the combination of solution heat treatment (at 520 °C for 1 h) and aging (at 165 °C for...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2020-07, Vol.791, p.139734, Article 139734
Main Authors: Paidar, M., Tahani, K., Vaira Vignesh, R., Ojo, O.O., Ezatpour, H.R., Moharrami, A.
Format: Article
Language:English
Subjects:
AA2024-T3
AA6061-T6
Aluminum alloys
Aluminum base alloys
Clinching
Dislocation density
Dwell time
Failure load
Fracture
Grain size
Hardness
Heat treating
Heat treatment
Mechanical properties
Microstructure
Modified friction stir clinching
Precipitation hardening
Precipitation heat treatment
Shear strength
Solution heat treatment
Strengthening
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Summary:This paper investigates the effect of dwell time and heat treatment on the modified friction stir clinched (MFSC) joint of AA2024-T3/AA6061-T6 Al alloys. The precipitation-hardening heat treatment method involves the combination of solution heat treatment (at 520 °C for 1 h) and aging (at 165 °C for 18 h) processes. The microstructure, failure load, hardness, and fracture behavior of the as-welded and heat-treated MFSC joints were investigated. TEM images show that re-precipitation of strengthening Al2CuMg and MgZn2 phases, dislocation density, and tangles are more pronounced in the heat-treated MFSC joint. A rise in dwell time increases the average grain sizes (1.39–6.65 μm), tensile-shear strength (101–133 MPa), and cross tension strength (59–88 MPa) of the MFSC welded 2024-T3/6061-T6 joints due to an upsurge in the in-process exposure time-induced heat input and inter-material flow. An increase in dwell time beyond 15 s is undesirable. It induces the formation of nugget cracks and micro-voids in the joints and an impaired joint failure load consequently ensues. Heat treatment processing further causes grain coarsening (2.48–9.15 μm) and improves the hardness (at the weld center), tensile-shear (146 MPa), and cross tension (102 MPa) failure strengths of the MFSC joints due to the re-precipitated strengthening phases.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2020.139734