AA6061 Alloy Research Articles

Cracks propagation mechanism of intergranular corrosion in Al–Cu–Li AA2195 alloys governed by constant relative humidity

Atmospheric corrosion of Al–Cu–Li AA2195 alloys was investigated in constant relative humidity (RH) controlled by saturated salt solutions. Corrosion process was governed by RH, especially for the transformation of corrosion products and crack growth. The deceleration corrosion kinetics and maximum pit depth were found to be in accordance with the power laws. The corrosion products gradually transformed from γ-Al(OH)3 and γ-AlOOH into NaAlCO3(OH)2 and γ-Al(OH)3 affected by RH and exposure time. The localized formation of pitting, filiform and exfoliation corrosion was induced by the presence of Cu/Mg/Li-containing secondary precipitates, including T1(Al2CuLi), θ'(Al2Cu) and S'(Al2CuMg) phases. Secondary precipitates with lower potential were prone to triggering intergranular corrosion. The primary cracks penetrated into the internal matrix along large angular grain boundaires. Secondary cracks propagated along corrosion channels of the stress-concentrated triple grain boundaries with higher schimd factors, larger Kernel average misorientation and higher geometrically necessary dislocation densities. A crack propagation mechanism controlled by RH was proposed.

Influence of Welding Parameters on Weld Timings, Temperature Variation and Mechanical Strength of Friction Stir Welded AA6061 and AA6082 Alloy

Influence of Welding Parameters on Weld Timings, Temperature Variation and Mechanical Strength of Friction Stir Welded AA6061 and AA6082 Alloy

The improvement of deformability in AA7075 alloy through cryogenic treatment and its correlation with microstructural evolution and FE modelling

Cryogenic treatment has high potential for improving the deformation behavior through the recrystallization at a low temperature. In this work, true stress–strain curves were obtained via compression tests to understand the deformation behavior of an AA7075 under cryogenic conditions. Results showed a significant improvement in the flow stress of AA7075, increasing from 260 to 560 MPa at the yield point. The strain hardening exponent (n) also increased from 0.25 to 0.35 after deformation at cryogenic temperatures. The presence of Al2CuMg phase influenced the deformation texture of the tested aluminum alloy, resulting in more elongated grains and fine sub-grains after deformation at cryogenic temperatures, due to the hindered recrystallization. Microstructure evolution after deformation at room and cryogenic temperatures was investigated using EBSD technique to characterize texture and recrystallized grains. The results indicated that the spacing of the high-angle grain boundaries (HAGBs) in the sample deformed at room temperature was slightly larger than in the cryogenically treated sample. The alloy deformed at the cryogenic temperature exhibited a higher strain hardening exponent (n = 0.35) compared to room temperature deformation (n = 0.25). Furthermore, finite element analysis supported the experimental findings, showing that the Plastic Equivalent Strain (PEEQ) of the model tested at cryogenic temperature was higher than at room temperature, attributed to grain refinement during low-temperature deformation. The calculated effective stress responses at cryogenic temperatures for the investigated flow stress aligned well with the experimental results. These new aspects and mechanisms of deformation of aluminum alloys at cryogenic temperatures can improve the formability of high-strength alloys in the future production of more complex and integrated lightweight components.

Experimental investigation on mechanical and tribological behavior features of gr/B 4 C reinforced AA7075 alloy matrix using induction stir casting

Experimental investigation on mechanical and tribological behavior features of gr/B ₄ C reinforced AA7075 alloy matrix using induction stir casting

Impact of intermetallics on strength-ductility synergy in friction stir welded WE43 -AA7075 dissimilar joints

The present study used underwater friction stir welding (FSW) to join WE43 alloy and AA-7075 alloy, offering better thermal control than conventional FSW. This technique resulted in grain refinement and the formation of dual phases with a more uniform distribution of beta (ß) and gamma (γ) phases. These microstructural improvements enhanced the tensile strength and ductility in the stir zone (SZ). Specifically, in Air-FSW, the strength was 51 MPa with 35 % joint efficiency, whereas in Water-FSW, it increased to 103 MPa with 64.3 % joint efficiency. The transverse Water-FSW joint exhibited a 7.36 % increase in elongation. The reduction in residual stress in Water-FSW enhanced ductility compared to traditional joints. The evenly distributed hard intermetallic compounds also contributed to the improvements in strength and elongation.

Effect of forming parameters on the corrosion performance of retrogression- and warm-formed AA7075 alloy sheets

ABSTRACT Retrogression forming (RF) and warm forming (WF) are used to remedy formability limitations of high-strength precipitation-hardened AA7075 alloy sheets. RF is a thermomechanical treatment combining retrogression heat treatment and the forming of initially peak-aged T6 temper. WF is a thermomechanical treatment of initially pre-aged temper. The present work examines the corrosion performance of retrogression- and warm-formed AA7075 alloy sheets by determining the optimal pre-aging temperature (80°C or 100°C), forming temperature (room temperature, 150–200°C), strain rate (1, 0.1, or 0.01 s−1), and heating rate (1.1 or 20°C·s−1) for conventional slow and novel fast-forming technologies. Several alternating- and direct-current electrochemical tests were administered, including electrochemical impedance spectroscopy, potentiodynamic polarization, and linear polarization resistance. Results showed that the corrosion performance (i.e., passive film and corrosion-resistant properties) of formed AA7075 sheets was directly proportional to pre-aging and WF temperatures, inversely proportional to the RF temperature, and mildly affected by strain/forming rate and heating rate during forming.

Improving intergranular cracking and stress corrosion cracking resistance of highly sensitized AA5083 Al-Mg alloy via reversion heat treatment

This study systematically examines the impact of reversion heat treatments (220–280 ℃ for 1 h) on the microstructure evolution, electrochemical corrosion, intergranular cracking (IGC) and stress corrosion cracking (SCC) of a severely sensitized (175 ℃/100 h) AA5083 alloy. Increasing the reversion temperature gradually enhances the corrosion resistance by dissolving the β′-Al3Mg2 phase, with the optimal treatment identified as 280 ℃/1 h. The βˊ phase maintains its planar film shape and continuously covers the grain boundaries after reversion treatment below 240 °C, but spheroidizes at the triple junctions at 260 °C. The morphology of the βˊ phase is dictated by grain boundary diffusion and interface diffusion. Reversion treatments improve SCC resistance by dissolving the β′ phase and reducing yield strength, attributed to anodic dissolution and hydrogen embrittlement mechanisms. This research offers valuable insights into the practical benefits of reversion treatments for Al-Mg alloy marine applications, addressing safety concerns related to sensitization.

Effects of interrupted aging T6I4 on hardness and fracture toughness of aeronautic AA7050 alloy

Effects of interrupted aging T6I4 on hardness and fracture toughness of aeronautic AA7050 alloy

Innovative hybrid and bifunctional rare earth complexes as corrosion inhibitors for AA2024 Alloy: Electrochemical and surface analysis enhanced by DFT/MD simulation

The hybrid inorganic–organic compounds, RE-thioglycolates (RE = Ce, Nd, Sm), were analyzed as effective green corrosion inhibitors of AA2024 alloy in 0.1 M NaCl solution. Utilizing Electrochemical Impedance Spectroscopy the protective inhibitory film on the alloy’s surface was affirmed, alongside the persistence of a natural oxide layer over time. These complexes demonstrated notable corrosion inhibition efficiency over immersion from 1 h to 3 days, with Sm-thiog retaining the high inhibition efficiency of over 95 % during 72 h. All RE-thioglycolates are mixed-type inhibitors, imparting resistance against both general and pitting corrosion.The presence of a protective inhibitory film on the AA2024 surface in NaCl solution has been substantiated through various analytical techniques including FTIR, SEM/EDS and XPS. A detailed examination of the differential inhibition exhibited by these bifunctional complexes is elucidated through theoretical calculations. The smallest difference of HOMO and LUMO orbitals for Sm-thiog of 3.21 eV indicates that this inhibitor attains the strongest donor–acceptor interactions with the metal surface. Predictions generated by Density Functional Theory/Molecular Dynamics simulations suggest the potential formation of diverse inhibitory species within the electrolyte. The corrosion inhibition mechanism proposed for RE-thioglycolates is grounded in electrochemical and theoretical insights, and subsequently validated through surface analysis methods.

On the formation trajectory of diverse corrosion morphologies associated with T phases in an Al-Cu-Li alloy

Four different types of localized corrosion morphologies associated with Al20Cu2Mn3 dispersoids (T phases) in an AA2195 alloy were traced using atom-resolved characterizations and quasi-in-situ experiments. At the atomic scale, we demonstrated that the rod-shaped T dispersoid is homogeneous within the grain but enriched with Cu on the side surfaces, leading to a depletion of T1 precipitates nearby and an abundance near the tips. This plays a significant role in the initiation of galvanic corrosion between T dispersoids and the matrix. Combined with heterogeneous nucleation, the subsequent redeposition of noble metal clusters results in four typical corrosion morphologies.

RETRACTED ARTICLE: Investigating the strength of butt-welded joints of AA6082 and AA5052 alloys through friction stir welding; the impact of tool tilt angle and feed rate

We, the Editors and Publisher of the Journal of Adhesion Science and Technology, have retracted the following article: Investigating the strength of butt-welded joints of AA6082 and AA5052 alloys through friction stir welding; the impact of tool tilt angle and feed rate. Journal of Adhesion Science and Technology, https://doi.org/10.1080/01694243.2023.2253631. Bhiksha Gugulothua, Rajasekaran Saminathan, A. Pradeep, Ankit Sharma, S. Vijayakumar, Prabhu Paramasivam, and N. Srinivasa Rao. (2023). Since publication, concerns have been raised by a third party about the integrity of the data presented in the article, as well as potential authorship concerns. When approached for an explanation, the authors have been unable to provide their original data to verify its authenticity. In addition, the authors have not fully responded to our questions regarding the process of the research conducted. We have been informed in our decision-making by editorial policies and the COPE guidelines. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Analyzing through-thickness corrosion homogeneity of stabilized AA5083 alloy after artificial sensitization

Through-thickness corrosion homogeneity of stabilized AA5083 alloy thick plate was investigated. For the as-received stabilized plates, no differences in corrosion behavior are evident in the specimens from different sampling positions along the thickness direction. However, in the plates after sensitization, the specimen from the surface position (T/10, SP) exhibits the highest degree of sensitization (DoS) and stress corrosion cracking (SCC) susceptibility, indicating the through-thickness corrosion inhomogeneity. Compared with interlayer position (3T/10, IP) and center position (T/2, CP), the higher grain stored energy and richer high angle grain boundaries (HAGBs) in SP specimens promote the formation of β phases (Al3Mg2) during the sensitization process. It results in a high coverage of β phases in the SP specimen and therefore induces severe corrosion.

Enhancing strength and ductility of graphene and ZrO2 nanoparticles hybrid reinforced AA2024 composite fabricate by laser powder bed fusion

The AA2024 aluminum alloy is difficult to manufacture by laser powder bed fusion (L-PBF) due to its crack sensitivity. This work introduces a novel crack-free graphene nano-platelets (GNPs) and ZrO2 nanoparticles hybrid-modified AA2024 alloy suitable for laser powder bed fusion (L-PBF). The columnar-to-equiaxed transformation caused by nanoparticles-inducing nucleation sites eliminates the cracks. A bimodal microstructure consists of coarse columnar grains and ultrafine equiaxed grains, which are formed in the as-built composites. Compared with the L-PBF prepared AA2024 alloy and 1 wt% ZrO2/AA2024 composite, the (0.2 wt% GNPs + 1 wt% ZrO2)/AA2024 composite exhibit the highest tensile strength of 382 MPa and elongation of 16 %. The introduction of GNPs and ZrO2 nanoparticles provide dual increment in both tensile strength and ductility compared with single ZrO2 nanoparticles modified AA2024. Following further T6 heat treatment, the tensile strength increased significantly to 624 MPa, but the elongation decreased dramatically to 5.6 %. In-depth analysis was provided of the strength and ductility improvements induced by GNPs/ZrO2 nanofiller in this investigation.

Influence of plasma electrolytic oxidation coating on reducing the corrosion rate of dissimilar FSW joint between AA5052 and AZ31 alloys by minimizing effect of different galvanic couple types

This study investigated the different aspects of macro/micro-galvanic corrosion behavior of plasma electrolytic oxidation coating (PEO) applied on a dissimilar joint. In this regard, AA5052 and AZ31 were joined by friction stir welding. Then, the dissimilar joints were simultaneously coated with different electrolyte conductivities and current densities through PEO process. Despite of coated samples, the stir zone (SZ) of uncoated sample was severely corroded due to macro-galvanic couple (AA5052/AZ31) and micro-galvanic couple (intermetallic compound/surrounding matrix). In the optimal coated sample (CD-350), the corrosion current density of SZ compared with uncoated sample dropped from 8.18 × 10−4 to 1.69 × 10−5 A/cm2. The ratio between corrosion current density of SZ and that of uncoupled anode that is demonstrating the severity of galvanic effect; was less than 5 (icorr SZ/iuncoupled anode = 4.17), therefore the various regions were totally compatible due to the effect of PEO coating on reducing different galvanic couple types. The corrosion rates for both heat-affected zone and base metal on each side of the coated samples were nearly identical, indicating the independence of the coating quality and properties from substrate microstructure. The findings revealed that rising electrolyte conductivity and current density led to the growth of coating thickness while the number of microspores decreased and their average diameter increased. Meanwhile, α-Al2O3, γ-Al2O3, and SiO2 amorphous formed on AA5052 side; and MgO, Mg2SiO4, and MgF2 on AZ31 side during coting process.

Effect of process parameters on weld geometry and mechanical properties in friction stir welding of AA2024 and AA7075 alloys

FSW joints are promising because they have a minimal heat input in welding and can limit the amount of intermetallic compound formation in dissimilar metals. Solid-state welding processes, particularly friction stir welding (FSW), are preferred for welding aluminium alloys due to their low heat input and ability to minimize intermetallic compound formation. This study conducted FSW trials on AA7075 and AA2024 alloys, each 4 mm thick. Parameters such as axial force, rotational speed, and traverse feed were adjusted while keeping other factors constant. The study analyzed weld geometry characteristics, including bead width and penetration depth. Angle distortions during FSW of thin plates in a butt joint were investigated. Additionally, the study examined the effects of FSW parameters on mechanical properties such as tensile strength and hardness immediately after welding. Microstructures of the welds were observed using optical microscopy (OM). The optimal mechanical properties are achieved at a rotational speed of 1000 rpm, a traverse feed of 30 mm/min, and an axial force of 10 kN. This optimal condition facilitates material flow around the pin at an ideal speed, ensuring adequate material filling and preventing tunnel formation. The stir zone's microstructure under these parameters exhibits a finely recrystallized structure with a significantly smaller grain size than the base material. Consequently, this enhances the joint's microhardness and tensile strength.

Microstructural Characterization, Tribological and Corrosion Behavior of H111 Hot-Rolled AA5754 after Homogenization and Aging.

In this study, the microstructural properties, wear resistance, and corrosion behavior of H111 hot-rolled AA5754 alloy before heat treatment, after homogenization, and after aging were examined. The microstructure was mainly composed of the scattered forms of black and gray contrast particles on the matrix and precipitations were observed at the boundaries of the grain. The as-rolled material exhibited a dense pancake-shaped grain structure, which is typical of as-rolled material. Observation along the L-direction did not yield distinct demarcations among the grains and was not uniformly distributed, with precipitates at the grain boundary. When they aged, there was a parallel increase in fine and huge black and gray contrast particles in the zone. Therefore, it could be stated that the amount of fine grains increased due to the rise in the homogenization process. The rolled base metal with the grain orientation was found to be parallel to the rolling direction. On the other hand, the coarse grains were clearly observed in the aging heat-treatment condition. The grains had an elongated morphology consistent with the rolling process of the metal before the heat-treatment process. The aged alloy had the highest hardness with a value of 86.83 HB; the lowest hardness was seen in the alloy before heat treatment with a value of 68.67 HB. The weight loss and wear rate of this material at the end of 10,000 m were, respectively, 1.01 × 10-3 g and 5.07 × 10-9 g/Nm. It was observed that the alloy had the highest weight loss and worst wear resistance before heat treatment. Weight loss and wear rates at the end of 10,000 m were, respectively, 3.42 × 10-3 g and 17.08 × 10-9 g/Nm. According to these results, the friction coefficients during wear were parallel and the material with the lowest friction coefficient after aging was 0.045. While the alloys corroded after aging showed more weight loss, the alloys corroded before heat treatment exhibited better corrosion behavior. Among the alloys, the least weight loss after 24 h was observed in the alloy that was corroded before heat treatment and this value was 0.69 × 10-3 mg/dm2. The highest weight loss was observed in the aged alloy with a value of 1.37 × 10-3 mg/dm2. The alloy before heat treatment, which corroded after casting, showed the lowest corrosion rate with a value of 0.39 × 10-3 mg/(dm2·day) after 72 h. The alloy that was corroded before heat treatment showed the best corrosion behavior by creating a corrosion potential of 1.04 ± 1.5 V at a current density of -586 ± 0.04 μA/cm2. However, after aging, the corroded alloy showed the worst corrosion behavior with a corrosion potential of 5.16 ± 3.3 V at a current density of -880 ± 0.01 μA/cm2.

Effect of laser power on weld microstructure of AA6082 sheets remote laser welded by circular beam wobbling

This paper aims to investigate the combined effect of circular beam wobbling and varying laser power on crack formation, weld geometry, microstructure and hardness during remote laser welding of AA6082 alloy. AA6082 sheets of 2 mm thickness were joined in overlap weld configuration using wobbling mode remote laser welding at 4 kW, 3 kW and 2.5 kW. Full penetration was achieved in the joints made at 4 kW and 3 kW, with severe crack formation. Welds at 2.5 kW showed partial penetration and no cracks; however, porosity formation was observed. While no significant change was observed in the dendritic structure and compound contents in fusion zones with full penetration, compound clusters dominated by Cu and Si elements were revealed in the seam root region at 2.5 kW (partial penetration). In full penetration welds (4 and 3 kW), the hardness decreased in the center of the fusion zone but increased from the surface to the root zone. However, for the partial penetration weld (2.5 kW), a limited change in the hardness values determined in the same direction was observed.

Microstructure, Mechanical, and Corrosion Performance of AA4343/AA3003/AA4343 Laminated Sheets Subjected to Cryorolling and Annealing

The effects of cryorolling (CR), hot rolling (HR), and different annealing temperatures on the microstructure, mechanical, and corrosion performance of AA4343/AA3003/AA4343 laminated sheets are studied. Compared with the HR samples, the microstructure of the CR samples presents a significant decrease in the size of elongated grains and significantly large second‐phase particles Al(Mn, Fe)Si in the AA3003 alloy. Grains in CR samples subjected annealing at 200–300 °C become finer. Increasing to 400–550 °C, the grains begin to grow, and the Si is diffused into the core layer. A comparison of HR and CR processing reveals a significant increase in the yield strength from 153 to 209 MPa and the ultimate tensile strength from 168 MPa to 217 MPa of the laminated sheet. Potentiodynamic polarization measurements and immersion tests are conducted to assess the corrosion morphology. After being immersed in a 3.5% NaCl solution for two weeks, the clad surface of the laminated sheet exhibits uniform corrosion products and pitting corrosion, which shows the pitting corrosion depth of the CR sample improved compared to the HR sample. The study suggests that both CR and annealing can be useful for enhancing the mechanical properties, and corrosion morphology of laminated sheets.

Electrochemistry and inhibitory evaluation of Musa paradisiaca particulates on AA6063 alloy for improved service life

Recent study has concentrated on the corrosion-inhibiting properties of numerous local plants and agrowaste particulates. This research investigates the corrosion inhibition properties of plantain peel particulates (PP) on AA6063 aluminum alloy in 1 M HCl environments. Through electrochemical analysis, adsorption examination, mathematical optimization and surface morphology examination, PP's efficacy as an inhibitor was assessed. Results indicate a reduction in corrosion rate from 31.2195 mm/year (control) to 10.678 mm/yr(year) (0.6 g PP). Adsorption isotherm studies reveal favorable adsorption characteristics, with Langmuir and Freundlich models showing high regression coefficients. The Gibbs free energy of adsorption (−18.3669 kJ/mol) suggests chemical adsorption. Empirical optimization using Design of Experiment (DOE) and ANOVA indicates optimal inhibition at 33 °C with 0.229 g PP concentration.

Anti-corrosion performance of ethyl dimethyl propylammonium bis (trifluoromethyl sulfonyl) imide (EDMPA-TFSI) for AA3003 alloy in acid chloride solutions in the presence and absence of potassium iodide

This work aims to evaluate the anti-corrosion potential of ethyl dimethyl propylammonium bis (trifluoromethyl sulfonyl) imide (EDMPA-TFSI)-ionic liquid on AA3003 alloy in 0.5 M HCl solution in the presence and absence of potassium iodide at ambient and elevated temperatures. The corrosion inhibition of AA3003 alloy by EDMPA-TFSI in the presence of potassium iodide was evaluated using hydrogen evolution measurements at 303 K and 333 K. The results show that in the absence of potassium iodide, EDMPA-TFSI decelerates AA3003 corrosion in an acidic medium with a maximum inhibition efficiency of 93.2 % and 90.5 % obtained at 303 K and 333 K respectively. In the presence of potassium iodide, 94.7 % and 89.8 % inhibition efficiencies were obtained at 303 K and 333 K, respectively. This adsorption behavior is concordant with the Langmuir adsorption isotherm and the corrosion process in the presence of EDMPA-TFSI shows consistency with first-order reaction kinetics. New information on the application of EDMPA-TFSI as a workable corrosion inhibitor is provided herein.