Liquid film formation and cracking during friction stir welding

Gerlich, A.P.; Shibayanagi, Toshiya

doi:10.1179/1362171811y.0000000005

Cited by 21 publications

(14 citation statements)

References 29 publications

(56 reference statements)

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“…Where warmer materials extrude nearby cool metals attributing to extrusion forces and motion of the tool pin, a bigger nugget zone is easy to form. However, at a rotation speed of 1180 rpm and lower welding speed of 95 mm/min, some liquation melting of aluminum substrate may occur due to excess high rate of the heat input per unit length [22]. These liquids smear and rub against the surface metals of each other beneath the shoulder face and then solidify just shortly after exposure to air during the forward motion of the shoulder.…”

Section: Macrostructurementioning

confidence: 99%

“…This is primarily due to the fact that welding speed governs the maximum temperature and the length of time to subject to the stirred materials during the welding. Rotation speed of tool determines the amount of heat produced per unit time, stirring, and mixing of the material around the pin [22,30]. The fine recrystallized grains could be coarsened obviously due to excess high temperature and longer affected time in the WNZ, when a low welding speed of 95 mm/min is used.…”

Section: Microhardness Profilementioning

confidence: 99%

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Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of 2060 aluminum lithium alloy

Mao

Liu

et al. 2015

Int J Adv Manuf Technol

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Two-millimeter-thick 2060 Al-Li alloy plates were friction stir welded under a welding speed of 95-150 mm/min and rotation speed of 750-1500 rpm. The effects of welding speed and rotation speed on formation quality, microstructure, secondary phase particles' transformation, and mechanical properties of the joints were investigated. The results show that defect-free joints are produced for varying friction stir welding (FSW) parameters, and nugget size increases firstly and then decreases with increasing rotation speed or decreasing welding speed. The weld nugget zones (WNZs) have fine dynamically recrystallized grains, and the size decreases to 7.9 μm with increasing rotation speed to 1180 rpm or decreasing welding speed to 118 mm/min, while the grains are coarsened at 1500 rpm or 95 mm/min. A similar trend occurs in the transformation of secondary phase particles, whose size is the smallest in WNZ at 1180 rpm-118 mm/min. All joints exhibit softened zones where the hardness is the lowest, and the joints fracture from WNZs or heat-affected zones. The joints welded at 1180 rpm-118 mm/min perform the highest ultimate tensile strength of 495 MPa, yield strength of 380 MPa, and elongation of 10.2 %. With increasing rotation speed or decreasing welding speed, the strengths and elongation of the joints increase firstly and then decrease.

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Section: Macrostructurementioning

confidence: 99%

Section: Microhardness Profilementioning

confidence: 99%

Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of 2060 aluminum lithium alloy

Mao

Liu

et al. 2015

Int J Adv Manuf Technol

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“…This phenomenon was observed in AA2024 friction stir spot welding (FSSW), and is produced by the melting of the Al 2 CuMg (S) phase, due to the elevated heating rate [31]. The formation of a local melting, during the FSW of AA2024-T351 was confirmed by Gerlich and Shibayanagi [32], as a consequence of the rotational speed that increase the temperature above the melting point of the S phase (437°C). This situation is avoided due to the low heating rates developed during the FSW (2.34-2.71°C/s), promoting the dissolution of the S phase as temperature rise.…”

Section: Energy Input and Thermal Cyclesmentioning

confidence: 92%

Effect of the energy input on the microstructure and mechanical behavior of AA2024-T351 joint produced by friction stir welding

Vale

Santos

et al. 2018

J Braz. Soc. Mech. Sci. Eng.

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Butt joints of AA2024-T351, with 6 mm thickness, were friction-stir-welded. The objective was to investigate the effects of the energy input on the microstructure and mechanical properties of the joints. The welded joints were tested employing a Mo-Va tool, with shoulder and pin diameter of 15 and 6 mm, respectively. The parameters were selected according to visual inspection of the welds, bending test, and microstructural analysis. Constant values of rotational speed and axial force were employed: 1000 rpm and 13 kN, respectively. The welding speed varied from 3 to 6 mm/s. Temperature measurements were performed along the welding process, analysis by optical microscope, microhardness, and bending tests. The process parameters selected resulted in butt joints with good characteristics, no microvoids, and full penetration. The base metal presented mainly S-type compounds, while in the HAZ thickening and loss of coherence of this precipitates are found. A more refined microstructure was found in the stir zone, based on the CDRX mechanism, with evidences of GDRX in the SZ/TMAZ (AS). As far away from the weld the indentation line is, lower is the hardness of the stir zone. The joints presented a similar increase in the mechanical resistance, with loss in ductility.

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“…For the aluminum, the liquation phenomenon has been reported mostly in arc welding processes since the liquid quantity is proportional to the heat input [64], [65]. In friction processes like FSW, this phenomenon has been observed in AA2024 and AA7075 alloys [66], but not in the 6000-alloy type, since the first ones present a wide range of solidification which promote the liquid presence even in low heat input processes. A particular case of liquation of AA6061 is presented in dissimilar friction welding process with magnesium alloy, due the formation of a reaction layer rich in Mg with melting temperatures of 814 K (541 °C), when the fusion temperature of the AA6061 ranges from 580 to 650 °C.…”

Section: Microstructural Characterizationmentioning

confidence: 99%

Weldability of Aluminum-Steel Joints Using Continuous Drive Friction Welding Process, Without the Presence of Intermetallic Compounds

Hincapié¹,

Salazar²,

Restrepo³

et al. 2020

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Weldability of aluminum-steel joints has been studied mainly to avoid the formation of IMC. Nowadays, there are two ways to control the effect of FexAly in welding: 1) the elimination of IMCs or 2) the generation of a thin and homogeneous layer of these phases. In this way, the present work explores the first route, manufacturing joints aluminum-steel using solid state welding process. In order to evaluate the effect of the welding parameters, temperature measures were carried out during the process as well as the microstructural evaluation using optical microscopy and SEM. Finally, the welded joints were subject to tensile strength tests to evaluate their mechanical behavior and try to stablish the nature of the interfacial bonding between both metals. The microstructural characterization of the joints does not reveal the formation of IMCs; this is attributed to the low temperature reached during the process, lower than 545 °C. The welded joint failures in the TMAZ, in the low hardness zone, product of the over aging of the precipitates β". The nature of the bonding in the interface is not clear yet, but it is considered that the atomic diffusion trough the interface and adhesive bonding favors the joint.

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Liquid film formation and cracking during friction stir welding

Cited by 21 publications

References 29 publications

Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of 2060 aluminum lithium alloy

Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of 2060 aluminum lithium alloy

Effect of the energy input on the microstructure and mechanical behavior of AA2024-T351 joint produced by friction stir welding

Weldability of Aluminum-Steel Joints Using Continuous Drive Friction Welding Process, Without the Presence of Intermetallic Compounds

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