Investigation of Thermal–Microstructure–Hardness Relationships in Dissimilar AA5052-H32/AA6061-T6 Friction Stir Welded Joints.
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| Title: | Investigation of Thermal–Microstructure–Hardness Relationships in Dissimilar AA5052-H32/AA6061-T6 Friction Stir Welded Joints. |
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| Authors: | Li, Wenfei1 (AUTHOR), Yakubov, Vladislav1,2 (AUTHOR), Karpenko, Michail3 (AUTHOR), Paradowska, Anna M.1,2,4 (AUTHOR) anna.paradowska@sydney.edu.au |
| Source: | Materials (1996-1944). Apr2026, Vol. 19 Issue 7, p1410. 20p. |
| Subjects: | Friction stir welding, Thermal analysis, Microstructure, Recrystallization (Metallurgy), Grain refinement, Hardness, Aluminum alloys |
| Abstract: | Highlights: All simulated peak temperatures were below the melting points of AA5052-H32 and AA6061-T6. The COMSOL model predicts thermocouple temperatures with errors within 10%. The highest temperatures in the nugget zone, combined with plastic deformation, induced dynamic recrystallisation. The minimum grain in the nugget zone was refined about eightfold relative to AA5052-H32. The AA5052-H32 TMAZ exhibited the minimum hardness with about 22% reduction. Friction stir welding (FSW) of dissimilar aluminium alloys often results in non-uniform microstructure and hardness distributions due to asymmetric temperature fields and material flow. The objective of this study is to establish a quantitative relationship between thermal history, microstructural evolution, and hardness distribution in dissimilar AA5052-H32/AA6061-T6 FSW joints by combining experimental characterisation with validated thermal modelling. AA5052-H32 and AA6061-T6 plates were welded under five different parameter sets. A thermal finite element model was developed in COMSOL Multiphysics to simulate temperature evolution during welding and was validated using embedded thermocouple measurements, with predicted peak temperatures ranging from 455 °C to 641 °C. Optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to characterise grain structure and dynamic recrystallisation (DRX) behaviour, while Vickers microhardness mapping was used to evaluate the local mechanical response. The results show that DRX occurred in the nugget zone (NZ), leading to significant grain refinement, with a minimum grain diameter of 6.07 µm, representing an approximately eightfold reduction compared with the base material AA5052-H32. In contrast, the thermo-mechanically affected zone (TMAZ) experienced limited recrystallisation due to insufficient plastic deformation and temperature. The lowest hardness was observed in the TMAZ on the AA5052-H32 side, with the hardness reduction of 22% primarily caused by work hardening loss. Hardness was also reduced by 34% on the AA6061-T6 side due to decreased precipitation strengthening caused by high temperatures. This combined experimental–numerical study provides a systematic thermal–microstructure–hardness framework for understanding and predicting local property variations in dissimilar FSW joints. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Highlights: All simulated peak temperatures were below the melting points of AA5052-H32 and AA6061-T6. The COMSOL model predicts thermocouple temperatures with errors within 10%. The highest temperatures in the nugget zone, combined with plastic deformation, induced dynamic recrystallisation. The minimum grain in the nugget zone was refined about eightfold relative to AA5052-H32. The AA5052-H32 TMAZ exhibited the minimum hardness with about 22% reduction. Friction stir welding (FSW) of dissimilar aluminium alloys often results in non-uniform microstructure and hardness distributions due to asymmetric temperature fields and material flow. The objective of this study is to establish a quantitative relationship between thermal history, microstructural evolution, and hardness distribution in dissimilar AA5052-H32/AA6061-T6 FSW joints by combining experimental characterisation with validated thermal modelling. AA5052-H32 and AA6061-T6 plates were welded under five different parameter sets. A thermal finite element model was developed in COMSOL Multiphysics to simulate temperature evolution during welding and was validated using embedded thermocouple measurements, with predicted peak temperatures ranging from 455 °C to 641 °C. Optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to characterise grain structure and dynamic recrystallisation (DRX) behaviour, while Vickers microhardness mapping was used to evaluate the local mechanical response. The results show that DRX occurred in the nugget zone (NZ), leading to significant grain refinement, with a minimum grain diameter of 6.07 µm, representing an approximately eightfold reduction compared with the base material AA5052-H32. In contrast, the thermo-mechanically affected zone (TMAZ) experienced limited recrystallisation due to insufficient plastic deformation and temperature. The lowest hardness was observed in the TMAZ on the AA5052-H32 side, with the hardness reduction of 22% primarily caused by work hardening loss. Hardness was also reduced by 34% on the AA6061-T6 side due to decreased precipitation strengthening caused by high temperatures. This combined experimental–numerical study provides a systematic thermal–microstructure–hardness framework for understanding and predicting local property variations in dissimilar FSW joints. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 19961944 |
| DOI: | 10.3390/ma19071410 |
