Effect of microstructure and precipitate formation on mechanical and corrosion behavior of friction stir processed AA6061 alloy using different cooling media

Proceedings of the Institution of Mechanical Engineers, Part C:

2021

Self Cite

In this study, friction stir welding (FSW) was performed on AA6061-T6 with and without brass interlayer. The FSW with interlayer was performed for various tool rotational speeds (600–1000 r/min) and at constant travel speed (25 mm/min). The defect-free joint with uniform distribution of brass particles in the stir zone (SZ) and formation of the uniform composite structure was observed at an intermediate optimized tool rotational speed of 800 r/min due to the proper material flow. A strong metallurgical bond between brass particles with aluminium alloy resulted in the formation of Al2Cu and Al4Cu9 strengthening intermetallic compounds (IMCs). The average grain size obtained for the weld with interlayer is smaller than weld without interlayer. The presence of the interlayer enhanced the hardness and the tensile strength compared to the weld without interlayer. This improvement in mechanical properties with interlayer is attributed to the formation and uniform distribution of strengthening IMCs. The corrosion analysis was carried out in 3.5% NaCl solution using immersion test and electrochemical polarization test. The weld with interlayer showed enhanced corrosion resistance than the weld without interlayer which is attributed to the formation of major Al2Cu IMC which has less activation energy for the corrosion process.

Section: Resultsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

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Effect of brass interlayer on microstructure, mechanical and corrosion behaviour of friction stir welded AA6061-T6 alloy

Nagu

Proceedings of the Institution of Mechanical Engineers, Part C:

2021

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“…6 Hence, FSW was also successfully employed to weld similar Al alloys and dissimilar materials such as Al to Mg, Al to Cu and Al to steel. [7][8][9] Although FSW produced fine and dynamically recrystallized grains, the weld thermal cycle causes thermal softening at the stir zone (SZ), reducing the corrosion resistance and weld joint strength. 10 The strength loss occurs mainly in precipitation-hardened alloys like AA6061 due to the precipitates dissolution and coarsening at elevated temperatures during FSW.…”

Section: Introductionmentioning

confidence: 99%

“…10 The strength loss occurs mainly in precipitation-hardened alloys like AA6061 due to the precipitates dissolution and coarsening at elevated temperatures during FSW. 11 The level of strength loss in the weld region during FSW of precipitation-hardened Al alloys is determined by the weld parameters, and it occurs even when optimum weld parameters are used [12][13][14] Various researchers showed that post-weld heat treatment (PWHT) could restore the strength loss of FSWed Al alloy joints. 15,16 From the literature survey, it was observed that optimization of FSW process parameters and PWHT are time consuming, and PWHT is not feasible in some practical applications.…”

Section: Introductionmentioning

confidence: 99%

Influence of brass interlayer and water cooling on microstructure, mechanical and corrosion behaviour of friction stir welded AA6061-T6 alloy

Nagu

Proceedings of the Institution of Mechanical Engineers, Part L:

2022

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This study investigated the effect of brass interlayer and water cooling on the mechanical properties and corrosion behaviour of friction stir welded AA6061 alloy. Although grain refinement was observed in the stir zone (SZ) of FSW without interlayer, strength loss occurred due to thermal softening. The insertion of a brass interlayer resulted in more grain refinement which could be attributed to brass particles acting as a nucleation site for further recrystallization. The weld strength with interlayer improved due to the formation of strengthening intermetallic compounds (IMCs) such as Al2Cu and Al4Cu9. However, the strength recovery is not attainable in a heat-affected zone (HAZ). Moreover, hard and brittle IMCs formed in SZ of weld with interlayer resulted in premature failure. Therefore, water cooling was used to enhance the hardness in HAZ. Very fine grains in SZ with a high fraction of high angle grain boundaries were obtained with water cooling FSW with interlayer, while HAZ softening was also reduced. Moreover, the water-cooling FSW with interlayer inhibited the formation of brittle intermetallics and decreased volume fraction of IMCs attributed to faster cooling rate. Thereby the strength of the overall weld joint was enhanced. The corrosion test was performed in 3.5% NaCl solution. The corrosion findings stated that the decrease in the number of intermetallics formed low galvanic coupling with aluminium matrix resulted in better corrosion resistance and minimum corrosion rate for water-cooled FSW than natural cooling.

Microstructure Evolution, Mechanical, and Corrosion Behavior of Cryogenic Friction Stir‐Processed AA2014 Alloy

Satyanarayana

2021

Adv Eng Mater

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Herein, a large‐area stir zone (SZ) is fabricated in AA2014 alloy via overlapping friction stir processing (FSP). The microstructure and texture evolution of AA2014 alloy during FSP is examined using electron backscattered diffraction (EBSD). EBSD maps reveal recrystallized fine grains with high‐angle grain boundaries in SZ due to dynamic recovery (DRV) and continuous dynamic recrystallization (C‐DRX). Severe plastic straining induced by the tool leads to the formation of the A‐(110) <111> component. The texture component is further investigated with X‐ray analysis, and the results are reported. Mechanical testing reveals that ductility significantly increases after FSP, whereas the hardness and strength remain lower than that of base metal (BM) due to thermal softening. Corrosion studies show that the corrosion attack is significantly controlled after FSP due to the development of a homogeneous fine‐grained structure and uniformly distributed fine precipitates.