Development of Metallographic Etchants for the Microstructure Evolution of A6082-T6 BFSW Welds

Tamadon, Abbas; Pons, Dirk J.; Sued, Kamil; Clucas, Don

doi:10.3390/met7100423

Cited by 33 publications

(52 citation statements)

References 30 publications

(48 reference statements)

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“…This is evident in an hourglass pattern in the cross section [24,26]. These hourglass borders distinguish the boundaries of the plastic deformation area (stirring zone) of the weld from substrate material.…”

Section: Literaturementioning

confidence: 99%

“…While studies of the microstructure [17,24] or internal flow of the weld [34,35] exist, study about the entry zone and the exit zone formation has been neglected in the literature. A characteristic of BFSW is the entry zone has a flashing protrusion prior to the weld stage [21].…”

Section: Literaturementioning

confidence: 99%

“…For BFSW, as a recent alternative, most of the work is focused on the material performance [27,28] or attempting to explain the formation mechanism of the internal defects based on metallurgical observations [24,[27][28][29]. There have been attempts to model the CFSW process using numerical simulation, e.g., as a thermo-mechanical phenomenon [30,31], but these efforts have not yet yielded a consolidated theory for the development of defects.…”

Section: Literaturementioning

confidence: 99%

“…Most of the published studies are focused on the process setup [9,10], tool development [10,15] or metallurgical and mechanical properties of the bobbin welds [22][23][24]. A predictive approach regarding the potential discontinuity defects (i.e., crack or void) is one of the necessities for process improvement which has not been described in the literature.…”

Section: Literaturementioning

confidence: 99%

“…The direct observation of the material flow behaviour in the weld is inherently difficult for a homogenous structure like the metal workpiece as it requires time consuming cutting, etching and polishing of the cross sections [24]. Alternatively, the approach taken was to confirm a plasticine analogue modelling process produces comparative weld defects to aluminium welds and then visualise flow patterns for various welding parameters using the plasticine analogue model.…”

Section: Approachmentioning

confidence: 99%

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Formation Mechanisms for Entry and Exit Defects in Bobbin Friction Stir Welding

Tamadon

Pons

Sued

et al. 2018

Metals

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Bobbin friction stir welding (BFSW) is an innovative variant for the solid state welding process whereby a rotating symmetrical tool causes a fully penetrated bond. Despite the process development, there are still unknown variables in the characterization of the process parameters which can cause uncontrolled weld defects. The entry zone and the exit zone consist of two discontinuitydefects and removing them is one of the current challenges for improving the weld quality. In the present research, the characteristic features of the entry and exit defects in the weld structure and formation mechanism of them during the BFSW processing was investigated. Using stacked layers of multi-colour plasticine the material flow, analogous to metal flow, can be visualised. By using different colours as the path markers of the analogue model, the streamline flow can be easily delineated in the discontinuity defects compared with the metal welds. AA6082-T6 aluminium plates and multi-layered plasticine slabs were employed to replicate the entry-exit defects in the metal weld and analogue samples. The fixed-bobbin tool utilized for this research was optimized by adding a thread feature and tri-flat geometry to the pin and closed-end spiral scrolls on both shoulder surfaces. Samples were processed at different rotating and longitudinal speeds to show the degree of dependency on the welding parameters for the defects. The analogue models showed that the entry zone and the exit zone of the BFSW are affected by the inhomogeneity of the material flow regime which causes the ejection or disruption of the plastic flow in the gap between the bobbin shoulders. The trial aluminium welds showed that the elimination of entry-exit defects in the weld body is not completely possible but the size of the defects can be minimized by modification of the welding parameters. For the entry zone, the flow pattern evolution suggested formation mechanisms for a sprayed tail, island zone and discontinuity-channel. For the exit zone a keyhole-shaped discontinuity is discussed as a structural defect.

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Section: Literaturementioning

confidence: 99%

Section: Literaturementioning

confidence: 99%

Section: Literaturementioning

confidence: 99%

Section: Literaturementioning

confidence: 99%

Section: Approachmentioning

confidence: 99%

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Formation Mechanisms for Entry and Exit Defects in Bobbin Friction Stir Welding

Tamadon

Pons

Sued

et al. 2018

Metals

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Evolution of microstructure and mechanical characteristics of friction stir welded ultrafine‐grained aluminum alloy 6082

Verma,

Padap

2023

Materialwissenschaft Werkst

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Bulk production of ultrafine‐grained material is in great demand presently. Ultrafine‐grained material can be synthesized using accumulative roll bonding, which is a prominent severe plastic deformation technique to develop such materials in bulk. There are further challenges in the fabrication of ultrafine‐grained material. Friction stir welding is a potential technique to join the ultrafine‐grained material while maintaining its mechanical and microstructural characteristics stability as no fusion is required. The present research work demonstrates the microstructural and mechanical characteristics of various welding zone after friction stir welding of ultrafine‐grained aluminum alloy 6082. The microstructural features were examined using optical microscopy and the electron back‐scattered diffraction technique. The variation in mechanical characteristics was observed using tensile and microhardness tests. The fractography of tensile specimens was studied to identify the mode of failure. The present study demonstrates the viability of friction stir welding to join ultrafine‐grained aluminum alloy 6082 developed by accumulative roll bonding. The ultrafine grain size of 0.52 μm was achieved after four accumulative roll bonding cycles. The microhardness of accumulative roll bonding processed samples and the tensile strength of the weld joint were increased about two times and 1.6 times respectively compared to the annealed sample.

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