Effect of welding speed on microstructure and mechanical properties of self-reacting friction stir welded 6061-T6 aluminum alloy

Liu, H.J.; Hou, Jian; Guo, Hongfei

doi:10.1016/j.matdes.2013.03.105

Cited by 150 publications

(81 citation statements)

References 19 publications

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“…Recrystallization in the TMAZ zone is dynamic and the resultant of mechanical operation and preheating can leave more dislocation in TMAZ relative to HAZ. In other words, although the grains in the TMAZ zone are larger than those in HAZ, the density of dislocations in TMAZ leads to an increase in hardness in this zone [21,22]. As the microhardness profiles show, compared to the samples welded at room temperature and preheated at 125°C, noticeably harder SZ has been formed at the joint interface of the specimen preheated at 75°C.…”

Section: Vickers Hardness Testmentioning

confidence: 97%

The effect of preheating on mechanical properties of friction stir welded dissimilar joints of pure copper and AA7075 aluminum alloy sheets

Safi

Amirabadi

Givi

et al. 2015

Int J Adv Manuf Technol

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In this paper, apart from introducing brand-new warm friction stir welding (WFSW) method, the effect of preheating on the mechanical properties of dissimilar friction stir welded copper/aluminum alloy sheets was investigated. Sheets of aluminum alloy 7075 and copper both with the thickness of 5 mm were used. The utilized welding tool was made of a H-13 tool steel with a threaded cone shape. Rotational speeds (ω) of 1200-1400 rpm and travel speeds (v) of 50-100 mm/min were used for better understanding of the effect of welding parameters on heat input. The sheets were kept in furnace with temperatures of 75 and 125°C, and welding was done afterward. At last, tensile test was done to compare the mechanical properties of the welds. The tensile test results showed 100 % increase in the strength of preheated joints in comparison with the non-preheated joints which were welded at room temperature. Considering the high thermal conductivity of both copper and aluminum, the reason of increase in strength of the joints could be related to the low temperature gradient between the weld zone and base metal because the heat gets out of the stir zone with lower steep. The maximum strength occurred for the specimen with the preheating of 75°C, rotational speed of 1300 rpm, and travel speed of 75 mm/min.

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Section: Vickers Hardness Testmentioning

confidence: 97%

The effect of preheating on mechanical properties of friction stir welded dissimilar joints of pure copper and AA7075 aluminum alloy sheets

Safi

Amirabadi

Givi

et al. 2015

Int J Adv Manuf Technol

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show abstract

“…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%

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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“…TMAZ and (d) Top shoulder The material in the advancing side (AS) moves to oppose the plate motion and is exposed to a more shear stress than that in the retreating side (RS). The grains in the nugget zone (NZ) characterized as fine grain structure due to the dynamic recrystallization in contrast to the base material (BM) microstructure [5]. There is no uniform flow pattern found in these zones.…”

Section: Microstructure Analysismentioning

confidence: 99%

Effect of Tool Pin Geometries on Friction Stir Welded Aa 6061

2018

IJMTER

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Abstract-The 3 mm thick aluminium alloy (AA) 6061-T6 was Friction Stir Welding (FSW) with three different tool pin geometries namely cylindrical, taper and bobbin at rotational speed of 1400rpm. FSW process was carried out under the welding speed of 40mm/min for cylindrical and taper tool pin whereas for bobbin tool pin FSW process was carried out under the welding speed of 80mm/min. The effect of welding speed on microstructure and mechanical properties of the joints was investigated. On comparing the results the welds carried out using bobbin tool pin shows the best mechanical properties. When the rotational speed increases, the tensile strength and maximum load of the welds also increases which shows that FSW weld at high rotational speed will be effective to weld AA6061. Hardness of the material increases with the increase of the speed. Due to the tensile strength and load of ability obtained, microstructure images for FSW welded plates using bobbin tool, taper tool at 1400 rpm was taken to investigate the grain orientation. Fine grains can be seen in the microstructure of bobbin tool FSW plates compared to the microstructure of cylindrical and taper tool FSW plates.

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Effect of welding speed on microstructure and mechanical properties of self-reacting friction stir welded 6061-T6 aluminum alloy

Cited by 150 publications

References 19 publications

The effect of preheating on mechanical properties of friction stir welded dissimilar joints of pure copper and AA7075 aluminum alloy sheets

The effect of preheating on mechanical properties of friction stir welded dissimilar joints of pure copper and AA7075 aluminum alloy sheets

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

Effect of Tool Pin Geometries on Friction Stir Welded Aa 6061

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