Factors Influencing the Environmental Behaviour of Aluminium-Lithium Alloys

Gray, A.

doi:10.1051/jphyscol:19873104

Cited by 13 publications

(8 citation statements)

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“…The precipitates itself have little influence on the pitting potential but on the kinetics of corrosion, either acting as local cathodes or being dissolved and disappear from the surface or cause selective corrosion. Figure 3 indicates the presence of higher amounts of anodic phases in alloy tempers with increasing aging time and these findings have also been reported by the authors and other researchers 5, 6, 8, 12, 23, 24, 27, 29.…”

Section: Resultssupporting

confidence: 86%

“…Aluminium alloys containing lithium are attractive and potential materials for the aerospace industry because of their attractive combination of 5–10% lower density, 15–25% higher elastic modulus and 10–15% more specific strength compared to the most widely used 2xxx and 7xxx series 1–3 alloys. However, AlLi alloys have reduced ductility, poor fracture toughness, marked anisotropy particularly of a non‐recrystallised structure, and are susceptible to environmental degradation 3–8. In addition to being fuel efficient, for longer service life, aircraft structures are also required to exhibit an ability to resist localised corrosion and environmental assisted cracking (EAC), for example stress corrosion cracking (SCC), hydrogen embrittlement (HE) and corrosion fatigue (CF).…”

Section: Introductionmentioning

confidence: 99%

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Study of aging and electrochemical behaviour of AlLiCuMg alloys

Ghosh

Mukhopadhyay

Konar

et al. 2012

Materials & Corrosion

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Aging study of 1441 and 8090 Al-Li-Cu-Mg alloys exhibited characteristic precipitation hardening phenomena. Potentiodynamic polarisation studies carried out on various tempers of the 1441 and 8090 Al-Li-Cu-Mg alloys in 3.5% NaCl, with a small amount of H 2 O 2 , and in 3.5% NaCl solution with pH 10 and 12 showed the shifting of open circuit potential (OCP) towards more negative potential and higher corrosion rate, with the increase of aging time. The OCP value has shifted anodically with addition of H 2 O 2 in 3.5% NaCl solution. Further, passivity phenomenon has been observed for all the alloy tempers in 3.5% NaCl solution at pH 10 and 12. The observation of OCP shift towards more negative potential and the higher corrosion rate with the increase of aging time has been attributed to the presence of higher amounts of anodic d (AlLi), S 0 (Al 2 CuMg) and T 1 (Al 2 CuLi) phases, studied by TEM, XRD and DSC methods.

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Study of aging and electrochemical behaviour of AlLiCuMg alloys

Ghosh

Mukhopadhyay

Konar

et al. 2012

Materials & Corrosion

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“…As with 2XXX series alloys, for which a stress-assisted intergranular corrosion mechanism is generally proposed, environmentally induced cracking in 8090 alloy might be also associated with a sharp attack on grain boundaries accelerated and localised by the applied load. The SCC behaviour of plate materials of AlLi alloys was similar to that of high strength alloys which should be substituted, such as 2014-T651, 2024-T351 or 7075-T651, revealing a low resistance in short transverse direction [42,114,116,123]. The SCC sensitivity depended upon the heat treatment, decreasing from underaged to peak-aged and further to overaged tempers [114].…”

Section: Al-li Alloysmentioning

confidence: 96%

“…The SCC behaviour of plate materials of AlLi alloys was similar to that of high strength alloys which should be substituted, such as 2014-T651, 2024-T351 or 7075-T651, revealing a low resistance in short transverse direction [42,114,116,123]. The SCC sensitivity depended upon the heat treatment, decreasing from underaged to peak-aged and further to overaged tempers [114]. However, the influence of isothermal aging was moderate compared to improvements achieved by overaging practices with 7XXX series alloys.…”

Section: Al-li Alloysmentioning

confidence: 99%

“…A short transverse threshold stress of about 100 MPa was determined for 8090 plate in the peak-aged temper T8771, whereas alloy 8090 in the underaged T8171 heat treatment exhibited a threshold stress below 100 MPa, as obtained from alternate immersion tests [116]. The SCC resistance of Al-Li-Cu-Mg-Zr alloys could be enhanced using more complex heat treatments, however, at sacrifice of strength, or by modifying the alloy composition by adding zinc [114,115]. The SCC initiation behaviour of Al-LiCu-Mg-Zr alloys was related to the electrochemical potential difference between matrix and grain boundary regions, which depended upon type and distribution of the precipitates both within the matrix and on grain boundaries, suggesting an anodic dissolution mechanism.…”

Section: Al-li Alloysmentioning

confidence: 99%

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Environmentally assisted cracking of aluminium alloys

Braun

2007

Materialwissenschaft Werkst

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Dedicated to Prof. Wolfgang Bunk on the occasion of his 80 th birthdayA short review of the stress corrosion cracking (SCC) behaviour of aluminium alloys is given. Mechanisms of environmentally assisted cracking are outlined. For aluminium alloys, in which stress corrosion cracks propagate predominantly along grain boundaries, anodic dissolution and hydrogen embrittlement have been proposed. Transgranular stress corrosion cracking occurring at severe loading conditions has found particular interest concerning localised corrosion-deformation interactions. Accelerated test methods for assessing the SCC behaviour are described, including the slow strain rate testing technique and the breaking load method. Results of recent studies on environmentally assisted cracking of aluminium alloys are summarised. Most of the work published in the last two decades has been on aluminium-lithium based alloys and improved high strength Al-Zn-Mg-Cu alloys in corrosion resistant retrogressed and re-aged tempers.Keywords: aluminium alloys, stress corrosion cracking, anodic dissolution, hydrogen embrittlement, testing methods

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Stress corrosion cracking behaviour of Al‐Li alloy 8090‐T8171 plate exposed to various synthetic environments

Braun¹

2004

Materials & Corrosion

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The stress corrosion cracking (SCC) behaviour of 8090‐T8171 plate material was investigated in short transverse direction performing constant load tests and constant extension rate tests under permanent immersion conditions. At an applied stress of 100 MPa, smooth round tensile specimens were exposed to synthetic environments containing chlorides and various nonhalide anions. Environment‐induced cracking was not observed in aqueous solutions of 0.6 M NaCl, LiCl, NH4Cl, or MgCl2. In 0.6 M NaCl solutions containing 0.06 M Na2SO4 or Na3PO4, the SCC behaviour of 8090‐T8171 plate was similar to that observed in pure 0.6 M NaCl solution. Sodium chloride solutions with additions of nitrate, hydrogen carbonate, or carbonate promoted stress corrosion cracking. Threshold stresses below 100 MPa were obtained from constant load tests using the latter environments. When sodium sulfite or sodium hydrogen phosphate was added, values being 100 MPa or slightly higher were determined. Lithium and ammonium present as cations in mixed salt electrolytes accelerated SCC failure. Lithium chloride solutions containing nitrate, hydrogen carbonate, carbonate, or sulfite were highly conducive to stress corrosion cracking. Very low SCC resistance was found for alloy 8090‐T8171 exposed to synthetic environments with additions of ammonium salts. Constant extension rate tests were carried out using notched tensile specimens. Displacement rates were in the range 2 × 10−6 − 2 × 10−5 mms−1. Aqueous 0.6 M NaCl solutions with additions of 0.06 M NH4HCO3, (NH4)2SO4, or Li2CO3 promoted environment‐induced cracking with 8090‐T8171 plate, as indicated by severe degradation of notch strength. The constant extension rate testing technique did not indicate SCC susceptibility using sodium chloride solutions containing sodium sulfate or lithium sulfate. For specimens exposed to substitute ocean water a slight degradation of notch strength was found at the lowest displacement rate applied.

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Factors Influencing the Environmental Behaviour of Aluminium-Lithium Alloys

Abstract: n i t i a t i o n and p r o p a g a t i o n i n Al-Li-Cu-Mg-Zr a l l o y s (e.g. 8090 and 8091

Cited by 13 publications

References 0 publications

Study of aging and electrochemical behaviour of AlLiCuMg alloys

Study of aging and electrochemical behaviour of AlLiCuMg alloys

Environmentally assisted cracking of aluminium alloys

Stress corrosion cracking behaviour of Al‐Li alloy 8090‐T8171 plate exposed to various synthetic environments

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