Influence of critical surface defects and localized competition between anodic dissolution and hydrogen effects during stress corrosion cracking of a 7050 aluminium alloy

Najjar, Denis; Magnin, T.; Warner, Terence E.

doi:10.1016/s0921-5093(97)00369-9

Cited by 171 publications

(84 citation statements)

References 29 publications

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“…[13][14][15][16][17][18][19][20][21][22][23][24][25] Typical PFZ widths, grain boundary precipitates and dislocation slip behaviors for various tempers are shown in Fig. 8-9.…”

Section: Microstructural Observationsmentioning

confidence: 99%

“…Several investigations have reported that the SCC mechanism involves anodic dissolution, [13][14][15] hydrogeninduced cracking (HIC), 5,13,[16][17][18] passive film rupture, 13,19) hydrogen embrittlement (HE), 14,15,20) magnesium segregation to grain boundaries [21][22][23] and a precipitate free zone (PFZ) along grain boundary. 24,25) However, the microstructural characteristics of Al-Zn-Mg high strength aluminum alloys are well known to have a strong influence not only on the mechanical properties but also on SCC susceptibility.…”

Section: Introductionmentioning

confidence: 99%

“…Generally, the increase of matrix precipitate size can reduce the susceptibility to SCC by changing the slip planarity, which also can effectively decrease hydrogen atoms trans-ported to the grain boundaries by dislocations to cause embrittlement. 15,17) On the other hand, the larger grain boundary precipitates can trap more atomic hydrogen to nucleate hydrogen bubbles, thereby decreasing the hydrogen concentration at grain boundary below a critical value to prevent intergranular SCC fracture. 26,27) Furthermore, the cathodic grain boundary precipitates grow by depleting solute atoms, broadening the anodic PFZ which contained no strengthen precipitation phase, was soft and weak.…”

Section: Introductionmentioning

confidence: 99%

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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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“…[13][14][15][16][17][18][19][20][21][22][23][24][25] Typical PFZ widths, grain boundary precipitates and dislocation slip behaviors for various tempers are shown in Fig. 8-9.…”

Section: Microstructural Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…A higher strain of 0.18% increased the rate about 7× compared to the unstressed condition. This effect of stress orientation on SCC resistance has been known for some time [1,5]. However, these data show the transition from IGC to IGSCC.…”

Section: Foil Penetration Experimentsmentioning

confidence: 77%

“…Localized corrosion of Al alloys in aqueous chloride solutions has been investigated using different techniques [1][2][3][4][5]. However, few techniques exist to study the kinetics of localized corrosion growth [6,7].…”

Section: Introductionmentioning

confidence: 99%

Effect of applied tensile stress on intergranular corrosion of AA2024-T3

et al. 2004

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The effect of uniaxial tensile stress on intergranular corrosion (IGC) of AA2024-T3 was studied using the foil penetration technique. Standard ASTM G49 fixed-displacement jigs were modified to allow the use of sheet samples, which were then attached to an electrochemical cell as in the foil penetration setup. The time for IGC to penetrate samples of varying thickness was monitored. This method provides a new approach to bridge the gap between IGC and intergranular stress corrosion cracking (IGSCC). Samples with various orientations relative to the rolling direction were studied in 1.0 M NaCl at controlled anodic potentials. Potentiodynamic polarization measurements indicated that the two breakdown potentials typically observed for AA2024-T3 were lower for stressed samples than for unstressed samples, and the current at a given potential was higher. The penetration rate depended on potential and was higher for stressed samples than for unstressed samples. The primary form of attack above the higher breakdown potential was IGSCC, whereas pitting dominated between the two breakdown potentials. Stress had a larger effect on penetration rate at higher applied potentials, indicating that pitting is less susceptible to the effects of stress than a properly oriented IGC crevice. The effects of stress on the penetration rates in various orientations were strongly linked to the anisotropic microstructure. X-ray microfocal radiography and optical microscopy of cross-sections were used to characterize IGSCC defects in thin penetrated foils. In certain orientations, crack faces were parallel rather than perpendicular to the stress direction as a result of the constraints of the microstructure on the orientation of the IGC. Implications for the mechanisms of IGC and IGSCC are discussed.

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Environmentally Induced Cracking of Aluminum and Its Alloys

Ghali¹

2010

Corrosion Resistance of Aluminum and Magnesium Alloys

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Influence of critical surface defects and localized competition between anodic dissolution and hydrogen effects during stress corrosion cracking of a 7050 aluminium alloy

Cited by 171 publications

References 29 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

Effect of applied tensile stress on intergranular corrosion of AA2024-T3

Environmentally Induced Cracking of Aluminum and Its Alloys

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