Exfoliation corrosion of friction stir welded dissimilar 2024-to-7075 aluminum alloys

Niu, Pengcheng; Li, W.Y.; Li, N.; Xu, Yaxin; Chen, D.L.

doi:10.1016/j.matchar.2018.11.002

Cited by 77 publications

(33 citation statements)

References 35 publications

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“…The bonding interface may have vortex type in case of poor combination of rotational speed and welding speed and it becomes more prominent for BMs with significant difference in the properties. Niu et al [71] investigated an AA2024-AA7075 joint and found that the top section of the SZ was composed of the BM of RS, whereas the middle and bottom sections by the BM of AS as shown in Figure 5. Kim et al [65] also showed that by placing the high strength Al alloy on the AS generates excessive agglomerations and defects due to limited material flow.…”

Section: Positioning Of Alloymentioning

confidence: 99%

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Friction Stir Welding of Dissimilar Aluminum Alloy Combinations: State-of-the-Art

Patel

Wang

et al. 2019

Metals

103

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Friction stir welding (FSW) has enjoyed great success in joining aluminum alloys. As lightweight structures are designed in higher numbers, it is only natural that FSW is being explored to join dissimilar aluminum alloys. The use of different aluminum alloy combinations in applications offers the combined benefit of cost and performance in the same component. This review focuses on the application of FSW in dissimilar aluminum alloy combinations in order to disseminate research this topic. The review details published works on FSWed dissimilar aluminum alloys. The detailed summary of literature lists welding parameters for the different aluminum alloy combinations. Furthermore, auxiliary welding parameters such as positioning of the alloy, tool rotation speed, welding speed and tool geometry are discussed. Microstructural features together with joint mechanical properties, like hardness and tensile strength measurements, are presented. At the end, new directions for the joining of dissimilar aluminum alloy combinations should guide further research to extend as well as to improve the process, which is expected to raise further interest on the topic.

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Section: Positioning Of Alloymentioning

confidence: 99%

“…Cross-sectional SEM macrostructure of the AA2024-AA77075 joints: (a) AS: AA2024 and (b) AS: AA7075, reproduced from[71], with permission from Elsevier, 2019.…”

mentioning

confidence: 99%

Friction Stir Welding of Dissimilar Aluminum Alloy Combinations: State-of-the-Art

Patel

Wang

et al. 2019

Metals

103

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“…While, the anodic phases, which are rich in Zn and Mg, have a 100–300 mV lower volt potential than surrounding matrix. Additionally, the potential difference between intermetallic phases and their surrounding matrix increases with the increasing alloying elements content [ 25 , 26 , 27 , 28 ]. Besides, a wider alloying element depletion zone with a more severe depletion would aggravate this electrochemical heterogeneity in alloys.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the sintered alloys containing more small powders exhibited a better corrosion resistance according to Figure 6 and Table 2 . The volt potential difference between intermetallic phases and their surrounding matrix depends on the composition difference, and significantly increases with the increasing content of alloying elements in second phases [ 25 , 26 , 27 , 28 ]. Thus, coarse grain zone in sintered alloys always exhibited higher driving force to resulting in passive film fracture and localized corrosion.…”

Section: Resultsmentioning

confidence: 99%

Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering

Tian

Kang

et al. 2020

Materials

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The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 μm in diameter and the small one was 10 ± 5 μm in diameter. The 7075 aluminium alloys was completely densified under the 500 °C sintering temperature and 60 MPa pressure. The large powders constituted coarse grain zone, and the small powders constituted fine grain zone in sintered 7075 aluminium alloys. The microstructural and microchemical difference between the large and small powders was remained in coarse and fine grain zones in bulk alloys after SPS sintering, which allowed for us to investigate the effects of microstructure and microchemistry on passive properties of oxide film formed on sintered alloys. The average diameter of intermetallic phases was 201.3 nm in coarse grain zone, while its vale was 79.8 nm in fine grain zone. The alloying element content in intermetallic phases in coarse grain zone was 33% to 48% higher than that on fine grain zone. The alloying element depletion zone surrounding intermetallic phases in coarse grain zone showed a bigger width and a more severe element depletion. The coarse grain zone in alloys showed a bigger electrochemical heterogeneity as compared to fine grain zone. The passive film formed on coarse grain zone had a thicker thickness and a point defect density of 2.4 × 1024 m−3, and the film on fine grain zone had a thinner thickness and a point defect density of 4.0 × 1023 m−3. The film resistance was 3.25 × 105 Ωcm2 on coarse grain zone, while it was 6.46 × 105 Ωcm2 on fine grain zone. The passive potential range of sintered alloys increased from 457 mV to 678 mV, while the corrosion current density decreased from 8.59 × 10−7 A/cm2 to 6.78 × 10−7 A/cm2 as fine grain zone increasing from 0% to 100%, which implied that the corrosion resistance of alloys increased with the increasing content of fine grains. The passive film on coarse grain zone exhibited bigger corrosion cavities after pitting initiation compared to that on fine grain zone. The passive film formed on fine grain zone showed a better corrosion resistance. The protectiveness of passive film was mainly determined by defect density rather than the thickness in this work.

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“…The tensile tests were carried out on several materials including aluminum alloys (AA6061-T621, AA2024-T3), magnesium alloys (ME20-H112, ZK60), and a mild steel specimen. The details of fabrication of AA6061-T621 [22], AA2024-T3 [23], and magnesium ME20-H112 [24] can be found elsewhere.…”

Section: Methodsmentioning

confidence: 99%

Effect of Auto-Tuning on Serrated Flow Behavior

Mohammed

Chen

2019

Metals

Self Cite

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The mechanical response of a servo-hydraulic testing system is affected by the stiffness of test specimens. An adaptive controller helps in auto-tuning the system by setting the optimal proportional-integral-derivative values for the subsequent test as the stiffness changes. This paper presents the effect of auto-tuning of various channels on the flow response of several commercial Al and Mg alloys and a mild steel. Strain-controlled monotonic tensile tests were performed at a given strain rate of 1 × 10−4 s−1 after auto-tuning of position, load, and strain channels in different combinations. Serrated flow or Portevin–Le Chatelier effect was observed in the Al alloys after auto-tuning of either position channel only or position and load channels. However, the serrations of Al alloys were shielded after further auto-tuning of strain channel. The stress-strain curves of Mg alloys and mild steel were observed to be basically free of serrations under any combinations of auto-tuning, which confirms that the serrated flow is a property of specific materials rather than a machine system noise.

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Exfoliation corrosion of friction stir welded dissimilar 2024-to-7075 aluminum alloys

Cited by 77 publications

References 35 publications

Friction Stir Welding of Dissimilar Aluminum Alloy Combinations: State-of-the-Art

Friction Stir Welding of Dissimilar Aluminum Alloy Combinations: State-of-the-Art

Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering

Effect of Auto-Tuning on Serrated Flow Behavior

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