The Postulated Mechanisms for Stress Corrosion Cracking of Aluminum Alloys: A Review of the Literature 1980-1989

Burleigh, Thomas D.

doi:10.5006/1.3585235

Cited by 174 publications

(88 citation statements)

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“…In the dislocation-assisted cracking mechanism, several researchers 2,13,[16][17][18] demonstrated that peakaged condition that had low resistance to SCC had long straight narrow slip bands after deformation, while overaged condition that had high resistance to SCC exhibited more homogeneous slip after deformation. A detailed analysis demonstrated that increasing the matrix precipitate can improve the SCC resistance of the alloys, because it can result in the change dislocation slip type from the planar slip to homogenous slip mode.…”

Section: Microstructural Observationsmentioning

confidence: 99%

“…[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%

“…The main microstructural change after RRA temper is a very fine distribution of 0 precipitates in the matrix similar to T6 temper, and a larger size of precipitates on grain boundaries distributed similarly to T7 temper. 5,10,11) The combination microstructures could effectively improve both SCC resistance and strength. In addition, two-step aging treatments are often employed in high-strength 7xxx series aluminum alloys to obtained maximum precipitation hardening and better stress-corrosion resistance.…”

Section: Introductionmentioning

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%

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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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Section: Microstructural Observationsmentioning

confidence: 99%

“…[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 2 more Smart Citations

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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“…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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