Mitigating Intergranular Stress Corrosion Cracking in Age-Hardenable Al-Zn-Mg-Cu Alloys

Krishnan, M.; Raja, V.S.; Shukla, Shweta; Vaidya, S. M.

doi:10.1007/s11661-018-4601-8

Cited by 24 publications

(5 citation statements)

References 39 publications

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“…7xxx series aluminium alloys are one of the most important aluminium alloys due to their high mechanical properties and low density. In the 7xxx series of aluminium alloys, the AA7050 is particularly popular in aerospace components that require high strength . AA7050 is an alloy with the same alloying elements (e.g., Zn, Mg, and Cu) similar to AA7075 but with a 0.11% Zr instead of 0.20% Cr.…”

Section: Introductionmentioning

confidence: 99%

Effects of retrogression and reaging heat treatment on the microstructure, exfoliation corrosion, electrical conductivity, and mechanical properties of AA7050

Özer

Kaya²,

Karaaslan

2019

Materials & Corrosion

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The effects of different retrogression times and temperatures on the microstructure, electrical conductivity, exfoliation corrosion (EXCO), and hardness of the 7050 aluminium alloy were compared with the T6 and T7451 condition. The EXCO solution was prepared in accordance with ASTM G34-01 standard and the samples were kept in the solution for 48 hr. Corrosion depths were examined by using scanning electron microscope (SEM) in the crosssections microstructure of the samples. The effect of EXCO on the material was investigated using stereo optical microscope images. In microstructure investigations, SEM and energy dispersive X-ray (EDX) analyses were used to determine the distribution and chemistry of the precipitates at the grain boundaries. The results show that retrogression and reaging (RRA) times and temperatures have significant effects on AA7050 EXCO. Especially after 200°C/ 30 min RRA process, it has been found that 7050 aluminium alloy has higher mechanical strength than T6 level and high corrosion resistance from T7451 level. According to the results of this study, it has been shown that there is a direct connection between electrical conductivity and EXCO. K E Y W O R D S AA7050, electrical conductivity, exfoliation corrosion, mechanical properties, retrogression and reaging

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Section: Introductionmentioning

confidence: 99%

Effects of retrogression and reaging heat treatment on the microstructure, exfoliation corrosion, electrical conductivity, and mechanical properties of AA7050

Özer

Kaya²,

Karaaslan

2019

Materials & Corrosion

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“…Most SCC cracking paths are occurred along the grain boundaries. Thus, the size, distribution and microchemistry of GBPs are mainly responsible for the SCC resistance of 7000 series aluminium alloys [27,28].…”

Section: Discussionmentioning

confidence: 99%

Comparison of strength, stress corrosion cracking and microstructure of new generation 7000 series aluminium alloys

Yuan

Tan

Chen

et al. 2021

Materials Science and Technology

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The strength, stress corrosion cracking (SCC), and microstructure of four typical new generation 7000 series aluminium alloys (AA7037, AA7097, AA7056, and AA7085) under three-stage aging heat treatment have been investigated. The results showed that AA7085 exhibited the highest SCC resistance while AA7037 displayed the lowest SCC resistance. In addition, AA7056 presented the higher strength and SCC resistance compared with AA7037. The more susceptible to SCC of new generation 7000 series aluminium alloys was mainly ascribed to the high Zn and low Cu content in grain boundary precipitates. The results provided a new insight for the composition design of new generation 7000 series aluminium alloys.

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“…Their strength can even match many grades of steels due to the coherent/semicoherent nano-scale η 00 /η 0 -MgZn 2 precipitates in the matrix produced during aging treatment (Deshpande et al, 1998;Ghosh et al, 2020) or in-process cooling (Kumar et al, 2017(Kumar et al, , 2018(Kumar et al, , 2021. However, 7xxx series of Al alloy are susceptible to SCC (Ajay Krishnan et al, 2018;Bobby-Kannan et al, 2003;Burns et al, 2010;Kannan et al, 2004). The GBPs within the precipitation free zones (PFZs), mainly η-Mg(Zn,Cu,Al) 2 , play an important role in initiating the SCC because they are anodic to the PFZs and preferentially undergo severe dealloying, especially in NaCl environments (Ajay Krishnan et al, 2018;Knight et al, 2010;Liu et al, 2015;Prabhuraj et al, 2017) The size, inter-distance and chemical composition of GBPs are some of the key parameters that control the SCC process (Huang et al, 2012;Kannan & Raja, 2006;Knight et al, 2010Knight et al, , 2015Liu et al, 2015;Peng et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…However, 7xxx series of Al alloy are susceptible to SCC (Ajay Krishnan et al, 2018;Bobby-Kannan et al, 2003;Burns et al, 2010;Kannan et al, 2004). The GBPs within the precipitation free zones (PFZs), mainly η-Mg(Zn,Cu,Al) 2 , play an important role in initiating the SCC because they are anodic to the PFZs and preferentially undergo severe dealloying, especially in NaCl environments (Ajay Krishnan et al, 2018;Knight et al, 2010;Liu et al, 2015;Prabhuraj et al, 2017) The size, inter-distance and chemical composition of GBPs are some of the key parameters that control the SCC process (Huang et al, 2012;Kannan & Raja, 2006;Knight et al, 2010Knight et al, , 2015Liu et al, 2015;Peng et al, 2011). Conventionally we use a TEM to fully characterize the microstructure of grain boundary and precipitates (Huang et al, 2012;Kannan & Raja, 2006;Zhou et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…However, there are limited tools to observe the GBPs microstructures. Although TEM is the most popular tool for GBPs observation bringing high resolution images with excellent contrast (Ajay Krishnan et al, 2018; Kannan & Raja, 2006; Zhou et al, 2021), there exist some limitations. First, the most adopted sample preparation method for AA7075 TEM observation—electropolishing—is sensitive to the variation of experimental parameters (i.e., voltage, current density, temperature, time, and flow rate), characteristics (thickness, conductivity, etc.)…”

Section: Introductionmentioning

confidence: 99%

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An advantageous imaging perspective for quantitative evaluation of 7075 aluminum alloy grain boundary precipitates using scanning electron microscope

Liu¹,

Tu²,

Chen

et al. 2022

Microscopy Res & Technique

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7075 Aluminum alloy (AA7075) samples undergone four aging sequences were examined using a scanning electron microscope (SEM) and a transmitted electron microscope (TEM). The measurements results validate the correlation between stress corrosion cracking (SCC) resistance and the size and inter‐distance of the grain boundary precipitates (GBPs). To evaluate the size and inter‐distance of GBPs, we demonstrate in this study a highly efficient SEM imaging technique that can unfold grain boundary in a two‐dimensional view. Compared to TEM, imaging with backscattered electrons in SEM (SEM‐BSE) is more advantageous for GBPs presentation and measurements. The major reason is that about 900 times more sampling area can be imaged with SEM from the same specimen for TEM observation, thus enabling frequent appearances of GBPs at normal top view perspective, a planar view best for GBPs quantitative analysis but not well‐documented. The acceleration tension of SEM for imaging was optimized at 10 kV with an information depth of around 330 nm. Research Highlights Scanning electron microscope (SEM) imaging using backscattered electrons is efficient for AA7075 grain boundary precipitate imaging. The precipitate size and inter‐distance can be more accurately measured with the perspective of normal top view under SEM than transmitted electron microscope.

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Mitigating Intergranular Stress Corrosion Cracking in Age-Hardenable Al-Zn-Mg-Cu Alloys

Cited by 24 publications

References 39 publications

Effects of retrogression and reaging heat treatment on the microstructure, exfoliation corrosion, electrical conductivity, and mechanical properties of AA7050

Effects of retrogression and reaging heat treatment on the microstructure, exfoliation corrosion, electrical conductivity, and mechanical properties of AA7050

Comparison of strength, stress corrosion cracking and microstructure of new generation 7000 series aluminium alloys

An advantageous imaging perspective for quantitative evaluation of 7075 aluminum alloy grain boundary precipitates using scanning electron microscope

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