Effect of microstructure on stress corrosion cracking of an Al-Zn-Mg-Cu alloy

Puiggali, M.; Zieliński, Andrzej; Olivé, Jean-Marc; Renauld, E.; Desjardins, D.; Cid, Manuel Sánchez

doi:10.1016/s0010-938x(98)00002-x

Cited by 153 publications

(65 citation statements)

References 12 publications

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“…The susceptibility of alloys to SCC has been shown to strongly depend on their chemical composition and heat treatment. 1) Speidel 2) also indicated that the SCC susceptibility of the precipitation hardening aluminum alloy increased with aging time, and the extreme susceptibility was occurred under peak-aging condition. While at over-aging condition, the SCC susceptibility is reduced but with loss of mechanical strength about 10-15% comparing to the T6 condition.…”

Section: Introductionmentioning

confidence: 99%

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Wang

Hsu

et al. 2007

Mater. Trans.

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The high strength Al-Zn-Mg alloy used in the aerospace industry is strengthened by coherent G.P. zones and semicoherent 0 phase. However, this series of aluminum alloys are susceptible to stress corrosion cracking (SCC), particularly when aged to the peak-aged state of T6 temper. In this study, the effect of microstructure on mechanical properties and stress corrosion cracking of the alloy was investigated for alloys tempered to T6, RRA, Two-Step and T7 conditions by tensile test in air, SCC test and polarization test in a 3.5%NaCl solution. It is shown that the improvement in SCC resistance correlates very well with the size of matrix precipitates and grain boundary precipitates. T7 temper can produce larger sizes of both the matrix precipitates and grain boundary precipitates than that of T6, RRA and Two-step tempers, causing a decrease in the length and density of dislocation lines, which results in the decrease of stress concentration at grain boundary and greatly improving the SCC resistance. The addition of Sc and Zr to high strength Al-Zn-Mg alloys has been found to simultaneously improve the tensile strength and SCC resistance.

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Section: Introductionmentioning

confidence: 99%

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Wang

Hsu

et al. 2007

Mater. Trans.

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“…Corrosion pits can not only act as stress concentration sites and increase the stress intensity factor at the bottom, but can also provide an appropriate environment where a concentration of ions and a change in pH value occurs. Connolly 21) and Puiggali 22) have shown that under SCC conditions, cracks were prone to nucleate at the bottom of corrosion pits of aluminium alloys. With aluminium alloy 6013, pitting readily occurred in solutions containing Cl À , which was most likely related to the active dissolution of the coarse intermetallics.…”

Section: 4mentioning

confidence: 99%

Stress Corrosion Cracking Behaviour of Excimer Laser Treated Aluminium Alloy 6013

Yue

Man

2008

Mater. Trans.

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The effect of excimer laser surface melting on the stress corrosion cracking behaviour of aluminium alloy 6013 has been investigated by means of a slow strain rate test at the open circuit potential, and at a constant anodic potential. After the laser treatment, a relatively thin nondentritic re-solidified layer, of the order of a few micrometres, and largely free of coarse constituent particles, has been produced. At the top surface of the re-solidified layer, an oxide-nitride bearing film, having a thickness of a couple of hundred nanometres, is present. The results of the slow strain rate test in a 3.5%NaCl solution showed that, in terms of total displacement to failure and corrosion current density, the stress corrosion resistance of the alloy was greatly increased by excimer laser melting. The superior stress corrosion resistance of the laser-treated material is attributed to the laser-formed oxide-nitride top film acting as a barrier and retarding the initiation of cracks.

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“…It is well documented that AA7xxx in the over-aged temper exhibits better stress corrosion cracking (SCC) resistance than in the peak aged condition [18][19][20][21][22][23][24]. Most SCC testing is done in a solution environment, and it was just shown that humidity has little effect on the sharp IGC fissure kinetics.…”

Section: Temper Effectsmentioning

confidence: 99%

Kinetics of sharp intergranular corrosion fissures in AA7178

Huang

Frankel

2007

Corrosion Science

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During service in structural aircraft applications, AA7178 has been found to develop sharp intergranular corrosion (IGC) fissures, a special form of attack. A new laboratory approach to quantify the kinetics of sharp IGC fissure growth was developed in this work. Sharp IGC fissures, similar to those formed in service, grew in samples that were given an electrochemical pre-treatment and then exposed in a humid environment. The time for the first sharp IGC fissure to penetrate the thin sample was determined by visual observation of the back side of the sample. The depth of the sharp IGC fissure was determined by serial sectioning. The kinetics measured by this approach did not represent the fastest rates, but rather the rates of long sharp IGC fissures. Relative humidity had no measurable effect on fissure kinetics, indicating that there was little connection of the local sharp IGC fissure region with the outside environment. AA7178 in the as-received and T7 conditions exhibited slower sharp IGC fissure rates than in the T6 condition. The sharp IGC fissures were found to be filled with corrosion products, which possibly exert a stress that could play an important role in driving fissure growth. It is suggested that the sharp IGC fissure could be a form of SCC.

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Effect of microstructure on stress corrosion cracking of an Al-Zn-Mg-Cu alloy

Cited by 153 publications

References 12 publications

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Stress Corrosion Cracking Behaviour of Excimer Laser Treated Aluminium Alloy 6013

Kinetics of sharp intergranular corrosion fissures in AA7178

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