Materials

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13 pages, 8383 KiB

Open AccessArticle

Interface Formation of Medium-Thick AA6061 Al/AZ31B Mg Dissimilar Submerged Friction Stir Welding Joints

by Tifang Huang, Zeyu Zhang, Jinglin Liu, Sihao Chen, Yuming Xie, Xiangchen Meng, Yongxian Huang and Long Wan

Materials 2022, 15(16), 5520; https://doi.org/10.3390/ma15165520 - 11 Aug 2022

Cited by 11 | Viewed by 1700

Abstract

The medium-thick Al/Mg dissimilar friction stir welding (FSW) joint has serious groove and cavity defects due to uneven thermal distribution in the thickness direction. The submerged friction stir welding (SFSW) was employed to decrease the peak temperature of the joint and control the [...] Read more.

The medium-thick Al/Mg dissimilar friction stir welding (FSW) joint has serious groove and cavity defects due to uneven thermal distribution in the thickness direction. The submerged friction stir welding (SFSW) was employed to decrease the peak temperature of the joint and control the thermal gradient of the thickness direction, which were beneficial in suppressing the coarsening of the intermetallic compounds (IMCs) layer and improving the weld formation. According to the SEM results, the thickness value of the IMC layer in the nugget zone and shoulder affect zone decreased from 0.78 μm and 1.31 μm in FSW process to 0.59 μm and 1.21 μm in SFSW process at the same parameter, respectively. Compared with the FSW process, SFSW improves the thermal accumulation during the process, which inhibits the formation of the IMCs and facilitates the material flow to form a mechanical interlocking structure. This firm interface formation elevates the effective contact area of the whole joint interface and provides a strong connection between the dissimilar metals. Thus, the ultimate strength of the 6 mm thick Al/Mg dissimilar SFSW joints was enhanced to 171 MPa, equivalent to 71.3% of AZ31B Mg alloys strength. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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15 pages, 4969 KiB

Open AccessArticle

Effect of Deformation on the Corrosion Behavior of Friction Stir Welded Joints of 2024 Aluminum Alloy

by Qiu Pang, Man Zhao and Zhi-Li Hu

Materials 2022, 15(6), 2157; https://doi.org/10.3390/ma15062157 - 16 Mar 2022

Cited by 1 | Viewed by 2145

Abstract

Friction stir welding (FSW) of aluminum alloys is an advanced manufacturing technology to realize lightweight bodywork. However, most studies only focus on the mechanical properties and corrosion behaviors of the welded joints. The effect of deformation on the corrosion behavior of FSWed joints [...] Read more.

Friction stir welding (FSW) of aluminum alloys is an advanced manufacturing technology to realize lightweight bodywork. However, most studies only focus on the mechanical properties and corrosion behaviors of the welded joints. The effect of deformation on the corrosion behavior of FSWed joints is unclear. In this work, the plastic deformation behavior was characterized using uniaxial tensile tests. The effect of deformation on the corrosion behavior of a 2024 aluminum alloy nugget was studied by using a Tafel polarization curve, electrochemical impedance spectroscopy, exfoliation corrosion test, scanning electron microscopy and energy dispersive spectrometer, and transmission electron microscopy. The results show that the corrosion resistance of FSWed joints with different deformation degrees can be ranked as: 0% > 7% > 10% > 4%, and an “inflection point” appears at 7%. The corrosion potential and current density at 7% are near the values at 0%, and the 7% sample shows less corrosion rate than all other deformation samples. Only pitting and bubbling occur in the sample in 96 h. With an increase in plastic deformation, the dislocations and dislocation rings increase, there is an increase in the surrounding winding precipitates. The impurity phase is cleaved by dislocations; a reduction in the size of the impurity phase with low chemical activity can be observed, resulting in an increase in corrosion resistance. However, the transgranular and intergranular cracks appear on the 10% deformation sample. They almost always develop along the grain boundaries after initiation, making them more susceptible to corrosion. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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11 pages, 5455 KiB

Open AccessArticle

Improving the Quality of Dissimilar Al/Steel Butt-Lap Joint via Ultrasonic-Assisted Friction Stir Welding

by Yu Chen and Fenghe Zhang

Materials 2022, 15(5), 1741; https://doi.org/10.3390/ma15051741 - 25 Feb 2022

Cited by 10 | Viewed by 2019

Abstract

A dissimilar AA7075/Q235 butt-lap joint was fabricated via ultrasonic-assisted friction stir welding (UaFSW), and the characteristics of the UaFSW joint were investigated systematically. The acoustoplastic effect of the ultrasonic vibration led to the softening of the materials and enhanced the material flow during [...] Read more.

A dissimilar AA7075/Q235 butt-lap joint was fabricated via ultrasonic-assisted friction stir welding (UaFSW), and the characteristics of the UaFSW joint were investigated systematically. The acoustoplastic effect of the ultrasonic vibration led to the softening of the materials and enhanced the material flow during welding, decreasing the volume of welding defects in the nugget zone of the UaFSW joint. With the help of ultrasonic vibration, a smooth and thin intermetallic compounds (IMCs) layer could generate along the Al/steel interface at the top of nugget zone, which possibly consisted of Al₅Fe₂ and Al₁₃Fe₄ phases. However, the positive effects of the ultrasonic vibration were weakened at low temperatures; consequently, the IMCs layer became discontinuous at the bottom of the nugget zone and the welding defects also formed. The ultrasonic vibration accelerated the dynamic recrystallization and refined the microstructures in the nugget zone due to the increased strain rate and stored energy. As a result, the UaFSW joint exhibited a better mechanical performance in comparison to the FSW joint, and the increment in the peak tensile load/elongation was more than twice. In addition, the UaFSW joint failed in the nugget zone along with the Al/steel interface, and the fracture mode was a mixture of ductile and brittle. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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17 pages, 19224 KiB

Open AccessArticle

Characteristics of Friction Plug Joints for AA2219-T87 FSW Welds

by Zhuanping Sun, Xinqi Yang and Shuxin Li

Materials 2022, 15(4), 1525; https://doi.org/10.3390/ma15041525 - 18 Feb 2022

Cited by 2 | Viewed by 1842

Abstract

In this study, Friction plug welding (FPW) for 8 mm thickness AA2219-T87 sheets were carried out, and defect-free joints were obtained. The geometric size of plug and plate hole, rotational speed and welding force exhibit significant effects on the weld formation. Meanwhile, it [...] Read more.

In this study, Friction plug welding (FPW) for 8 mm thickness AA2219-T87 sheets were carried out, and defect-free joints were obtained. The geometric size of plug and plate hole, rotational speed and welding force exhibit significant effects on the weld formation. Meanwhile, it is concluded that significant inhomogeneity of microstructure and mechanical properties exists in FPW joints. The recrystallization zone has the highest mechanical properties owing to the fine equiaxed grains and uniformly distributed θ precipitates. The entire plug, thermo-mechanically affected zone and nugget thermo-mechanically affected zone closed to the bonding interface are significantly softened due to the deformation of the grains and θ’ precipitate dissolution. The ultimate tensile strength (UTS) and elongation of the FPW joints can reach 359 MPa and 7.3% at 77 K and 305 MPa and 5% at 298 K, respectively. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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10 pages, 8151 KiB

Open AccessArticle

Effect of Welding Speed on Microstructure Evolution and Mechanical Properties of Friction Stir Welded 2198 Al-Cu-Li Alloy Joints

by Wenyan Zhang, Yuqing Mao, Ping Yang, Ning Li, Liming Ke and Yu Chen

Materials 2022, 15(3), 969; https://doi.org/10.3390/ma15030969 - 27 Jan 2022

Cited by 12 | Viewed by 2071

Abstract

In the present study, 2198 Al-Cu-Li alloys were successfully friction stir welded by using various welding speed ranges of 90~180 mm/min with an invariable rotation speed of 950 r/min. The effect of welding speed on microstructure evolution and mechanical properties of the joints [...] Read more.

In the present study, 2198 Al-Cu-Li alloys were successfully friction stir welded by using various welding speed ranges of 90~180 mm/min with an invariable rotation speed of 950 r/min. The effect of welding speed on microstructure evolution and mechanical properties of the joints was investigated. The results show that, with the welding speed decreasing, the size of the nugget zone (NZ) first increases and then decreases due to different welding temperatures. At a welding speed of 150 mm/min, the size of the NZ in all joints is the biggest and the “S” curve disappears. The equiaxed grains are finer, attributed to a higher degree of dynamic recrystallization, and a larger number of fine reprecipitated phase (δ’, β’ phases) particles are dispersively distributed in the NZ. Correspondingly, the joints have the highest tensile properties, and the tensile strength, yield strength and elongation are, respectively, 406 MPa, 289 MPa and 7.2%. However, compared to the base material, the tensile properties of all joints are reduced because a greater amount of δ’ and β’ phases particles are dissolved in the NZ. Only the joints produced at 150 mm/min are fractured in the TMAZ with detected deep dimples and tearing ridges, and a significant necking phenomenon is observed, which indicates a complete ductile fracture mode. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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10 pages, 7879 KiB

Open AccessArticle

Diffusion Bonding of Al-Mg-Si Alloy and 301L Stainless Steel by Friction Stir Lap Welding Using a Zn Interlayer

by Ji-Hong Dong, Hua Liu, Shu-De Ji, De-Jun Yan and Hua-Xia Zhao

Materials 2022, 15(3), 696; https://doi.org/10.3390/ma15030696 - 18 Jan 2022

Cited by 8 | Viewed by 2002

Abstract

Friction stir lap welding (FSLW) is expected to join the hybrid structure of aluminum alloy and steel. In this study, the Al-Mg-Si aluminum alloy and 301L stainless steel were diffusion bonded by FSLDW with the addition of 0.1 mm thick pure Zn interlayer, [...] Read more.

Friction stir lap welding (FSLW) is expected to join the hybrid structure of aluminum alloy and steel. In this study, the Al-Mg-Si aluminum alloy and 301L stainless steel were diffusion bonded by FSLDW with the addition of 0.1 mm thick pure Zn interlayer, when the tool pin did not penetrate the upper aluminum sheet. The characteristics of lap interface and mechanical properties of the joint were analyzed. Under the addition of Zn interlayer, the diffusion layer structure at lap interface changed from continuous to uneven and segmented. The components of the diffusion layer were more complex, including Fe-Al intermetallic compounds (IMCs), Fe-Zn IMCs and Al-Zn eutectic. The largely changed composition and thickness of uneven and segmented diffusion layer at the lap interface played a significant role in the joint strength. The tensile shear load of Zn-added joint was 6.26 kN, increasing by 41.3% than that of Zn-not-added joint. These two joints exhibited interfacial shear fracture, while the Zn interlayer enhanced the strength of diffusion bonding by extending the propagation path of cracks. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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17 pages, 5505 KiB

Open AccessArticle

Assessment of the Corrosion Behavior of Friction-Stir-Welded Dissimilar Aluminum Alloys

by Rami Alfattani, Mohammed Yunus, Ahmed F. Mohamed, Turki Alamro and Mohamed K. Hassan

Materials 2022, 15(1), 260; https://doi.org/10.3390/ma15010260 - 30 Dec 2021

Cited by 14 | Viewed by 2380

Abstract

The fuel consumption of high-density automobiles has increased in recent years. Aluminum (Al) alloy is a suitable material for weight reduction in vehicles with high ductility and low weight. To address environmental problems in aircraft and maritime applications, in particular rust development and [...] Read more.

The fuel consumption of high-density automobiles has increased in recent years. Aluminum (Al) alloy is a suitable material for weight reduction in vehicles with high ductility and low weight. To address environmental problems in aircraft and maritime applications, in particular rust development and corrosion, the current study assesses the corrosion behavior during friction stir welding (FSW) of two dissimilar Al alloys (AA6061 and AA8011) in various corrosive conditions using salt spraying and submersion tests. Two acidic solutions and one alkaline solution are used in these tests, which are performed at room temperature. The two specimens (AA6061 and AA8011) and the weld region are suspended in a salt spraying chamber and a 5 wt.% NaCl solution is continually sprayed using the circulation pump for 60 h, with the specimens being weighed every 15 h to determine the corrosion rates. According to the salt spraying data, the weld zone has a higher corrosion resistance than the core components. For twenty-eight days, individual specimens are submerged in 3.5 wt.% HCl + H₂O and H₂SO₄ + H₂O solutions and seawater. The weld area specimens exhibit stronger corrosion resistance than the base material specimens, and weight loss in the saltwater medium is lower when compared to the other test solutions, according to the corrosion analysis. The scanning electron microscope (SEM) analysis demonstrates that the base metal AA8011 is considerably corroded on its surface. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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14 pages, 7079 KiB

Open AccessArticle

Influence of Welding Speed on Microstructure and Mechanical Properties of 5251 Aluminum Alloy Joints Fabricated by Self-Reacting Friction Stir Welding

by Shikang Gao, Li Zhou, Guangda Sun, Huihui Zhao, Xiaolong Chu, Gaohui Li and Hongyun Zhao

Materials 2021, 14(20), 6178; https://doi.org/10.3390/ma14206178 - 18 Oct 2021

Cited by 2 | Viewed by 1894

Abstract

In the present study, 8 mm-thick 5251 aluminum alloy was self-reacting friction stir welded (SRFSW) employing an optimized friction stir tool to analyze the effect of welding speed from 150 to 450 mm/min on the microstructure and mechanical properties at a constant rotation [...] Read more.

In the present study, 8 mm-thick 5251 aluminum alloy was self-reacting friction stir welded (SRFSW) employing an optimized friction stir tool to analyze the effect of welding speed from 150 to 450 mm/min on the microstructure and mechanical properties at a constant rotation speed of 400 rpm. The results indicated that high-quality surface finish and defect-free joints were successfully obtained under suitable process parameters. The microhardness distribution profiles on the transverse section of joint exhibited a typical “W” pattern. The lowest hardness values located at the heat-affected zone (HAZ) and the width of the softened region decreased with increasing welding speed. The tensile strength significantly decreased due to the void defect, which showed mixed fracture characteristics induced by the decreasing welding speed. The average tensile strength and elongation achieved by the SRFSW process were 242.61 MPa and 8.3% with optimal welding conditions, and the fracture surface exhibited a typical toughness fracture mode. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Nonferrous Metals and Their Composites)

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