Effect of welding flash on the corrosion of friction stir spot welded AZ31B

Savguira, Yuri; Liu, W. H.; North, T. H.; Thorpe, Steven J.

doi:10.1002/maco.201609182

Cited by 6 publications

(19 citation statements)

References 47 publications

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“…Owing to the effect of microgalvanic corrosion, pitting corrosion occurred in the corrosion surface. Similar results can be found in many previous studies regarding the corrosion behavior of Mg–Al–Zn alloys …”

Section: Resultssupporting

confidence: 92%

Evaluation of corrosion resistance of multipass friction stir processed AZ31 magnesium alloy

Liu

Shen

Tang

et al. 2019

Materials & Corrosion

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Multipass friction stir processing (FSP) is an effective method to produce a homogeneous microstructure and enhance the mechanical properties of magnesium (Mg) alloys. However, few studies have concentrated on the variation of corrosion resistance of Mg alloys during multipass FSP. Electrochemical alternating current (AC) impedance, polarization behavior, hydrogen evolution, and corrosion morphology were used to investigate the effects of subsequent passes on the corrosion resistance of FSP AZ31 plates. A quasi‐in‐situ observation of the growth of corrosion products was carried out to further study the corrosion behaviors of FSP AZ31 alloy. It is found that subsequent passes could further reduce the grain size of FSP AZ31 alloy and result in an increase in the hardness compared with the first pass. Moreover, subsequent passes are beneficial to the improvement in the corrosion resistance of AZ31 alloy. Pitting corrosion occurs in FSP AZ31 plates, which has not changed after subsequent passes.

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Section: Resultssupporting

confidence: 92%

Evaluation of corrosion resistance of multipass friction stir processed AZ31 magnesium alloy

Liu

Shen

Tang

et al. 2019

Materials & Corrosion

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“…Unlike AZ31 that has been previously shown to exhibit complete dissolution of β-Mg 17 Al 12 particles as a result of welding, AZ80 exhibited only a partial dissolution of these particles. 12 The difference is likely related to their size in which they are initially present in the base metal. The nano sized β-Mg 17 Al 12 particles in AZ31 would be expected to dissolve faster than the micron sized particles in AZ80.…”

Section: Resultsmentioning

confidence: 99%

“…In similar welds, the noble stir zone forms a galvanic couple with the active base metal, 12 and therefore were not included here. causing preferential dissolution at the periphery of the weld nugget.…”

Section: Resultsmentioning

confidence: 99%

“…Finally, when the exposure time increased even further (43 hours) the corrosion resistance of both alloys increased due to the presence of the quasipassive film, and the overall number of bubbles decreased. 12,17 The bubbles that remained on the surface were preferentially located on the AZ80 side, with some preference being given to sites near the dissimilar interface. Similar observations were made on the corresponding uncoupled based metals ( Figure 9).…”

Section: Resultsmentioning

confidence: 99%

“…12 Each region was investigated using two magnifications (x300, and x1,000), and for each region two micrographs at the lower magnification, and eight micrographs at the higher magnifications were used in the analysis. The micrographs were analyzed using image processing software to measure the size of the particles of each secondary phase in the micrograph.…”

Section: Methodsmentioning

confidence: 99%

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Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Savguira

North

Thorpe

2018

J. Electrochem. Soc.

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Corrosion of dissimilar friction stir welds (FSW) made in AZ31/AZ80 magnesium alloys was investigated using the scanning reference electrode technique (SRET), and microcapillary polarization technique, complemented by optical and SEM/EDX microscopy. The corrosion rate of the base metals along with the welded specimen was estimated by mass loss testing. The stir zone material in both alloys showed a higher corrosion potential than the base metal due to the partial dissolution of β-Mg 17 Al 12 and Al-Mn particles. The basic corrosion mechanism in dissimilar welds was determined to be different from that of a similar joint. The corrosion behavior of the dissimilar FSW joint was governed by the galvanic coupling of the two alloys, and not by the microstructural evolution occurring during the welding process. The corrosion behavior of the joint was governed by the galvanic coupling between the α-Mg matrix in AZ31 and the Al-rich intermetallics in AZ80. The welded specimens exhibited the highest corrosion rate, while AZ80 was the most corrosion resistant material. Magnesium alloys can be successfully joined by friction stir welding (FSW) to achieve excellent mechanical integrity in completed welds. 1,2 One challenge arising from the utilization of this joining method is an increased susceptibility to localized corrosion in the material immediately adjacent to the welded joint. 3-6 Previous microcapillary polarization and scanning reference electrode technique (SRET) studies have revealed that the stir zones in AZ31B spot and seam welds are more cathodic than the bulk material. [3][4][5][6] Due to the difference in electrochemical potentials, a macrogalvanic cell is formed causing pitting corrosion in the thermo-mechanically affected zone (TMAZ) and the heat affected zone (HAZ) regions, which are located between the noble stir zone and the active base metal. 5 The differences in the electrochemical behavior of different regions in completed joints have been related to their microstructural evolution that occurred during the welding operation. The stir zone microstructure comprised a dynamically recrystallized matrix which was nominally devoid of intermetallics. The increase in the corrosion potential of the stir zone has been attributed to the dissolution of β-Mg 17 Al 12 and Al-Mn particles via two mechanisms: 4,5 1. Dissolution of intermetallics, which increases the concentration of Al in the α-Mg matrix, resulting in a higher corrosion potential of this region, 7 and 2. The absence of the intermetallics, which eliminates the microgalvanic coupling between the intermetallic particles (IMPs) and the α-Mg matrix, and reduces the susceptibility of the welded joint to localized pitting corrosion. [8][9][10][11] Many industrial applications require joining of dissimilar alloys, and therefore it is essential to understand the influence of the welding process on the corrosion behavior of dissimilar joints. It is currently unknown whether the corrosion behavior of dissimilar welds is governed by the microstructural changes o...

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Corrosion behavior of friction stir‐welded AZ31 Mg alloy after plastic deformation

Liu

Zhang

et al. 2021

Materials & Corrosion

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Postweld plastic deformation was reported to be able to largely enhance the mechanical properties of friction stir‐welded (FSW) Mg alloys by changing microstructures in the regions with a soft‐oriented texture. However, few studies have concentrated on the effects of postweld plastic deformations on the corrosion behavior of FSW Mg alloys, which has an impact on their application. In the present study, electrochemical measurements, hydrogen evolution, and mass loss tests were used to study the influences of postweld compression along the transverse direction and subsequent annealing on the corrosion rate of FSW AZ31 Mg alloys. It was found that owing to the grain refinement in the weld zones, an improvement in the corrosion resistance and hardness was observed in the FSW AZ31 sample compared to the base metal (BM) sample. Postweld compression was very harmful to the corrosion resistance of the FSW AZ31 alloys. On the basis of the mass loss results, the corrosion rate of the compressed FSW sample was ~17.62 mm/year, which was ~8.99 times that of the FSW sample (~1.96 mm/year). Subsequent annealing could slightly reduce the corrosion rate of the compressed FSW AZ31 plates, whereas the corrosion rate of the FSW‐C‐T sample (~13.63 mm/year) was much worse than that of the BM sample (~4.73 mm/year).

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Effect of welding flash on the corrosion of friction stir spot welded AZ31B

Cited by 6 publications

References 47 publications

Evaluation of corrosion resistance of multipass friction stir processed AZ31 magnesium alloy

Evaluation of corrosion resistance of multipass friction stir processed AZ31 magnesium alloy

Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Corrosion behavior of friction stir‐welded AZ31 Mg alloy after plastic deformation

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