Mechanistic Studies of Intergranular Stress Corrosion Cracking in Al-Mg Alloys under Atmospheric Exposure Conditions

CORROSION ◽  
10.5006/2853 ◽  
2018 ◽  
Vol 74 (10) ◽  
pp. 1117-1131 ◽  
Author(s):  
P.J. Steiner ◽  
J.T. Burns
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Stress Corrosion Cracking ◽  
Close Correlation ◽  
Open Circuit ◽  
Corrosion Cracking ◽  
Intergranular Stress Corrosion ◽  
Chemistry Development ◽  
Intergranular Stress Corrosion Cracking

The effect of atmospheric environments on the intergranular stress corrosion cracking (IG-SCC) behavior of AA5083-H131 and AA5456-H116 was investigated using fracture mechanics-based testing, high-fidelity monitoring of crack growth kinetics, and electrochemical potential measurements. The IG-SCC susceptibility was found to decrease in atmospheric environments as compared to full immersion at −0.8 VSCE. Critically, the decrease in IG-SCC susceptibility was most prevalent for higher levels of sensitization and the more susceptible AA5083-H131 alloy. These results are analyzed in the context of a coupled anodic dissolution and H-embrittlement mechanism, wherein the reduction in IG-SCC susceptibility in the atmospheric environments results from cathodic limitation of the governing IG-SCC mechanism, leading to a decrease in the dissolution at the crack tip, a less aggressive crack chemistry development, and thus lower levels of H production. A close correlation between the open circuit potential of the bulk surface and the crack growth kinetics was observed for environments without a set potential, and correlates well with known potential-dependent IG-SCC observations.

In-Situ Observations of Intergranular Stress Corrosion Cracking

2008 ◽  
Author(s):  
Jonathan A. Duff ◽  
Thomas J. Marrow
Keyword(s):  
Digital Image Correlation ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Digital Image ◽  
Corrosion Cracking ◽  
Image Correlation ◽  
Intergranular Stress Corrosion ◽  
Intergranular Stress Corrosion Cracking

The development and validation of predictive models for intergranular stress corrosion cracking requires knowledge of short crack growth kinetics in response to mechanical driving forces. A new experimental method for in-situ observation of the early stages of crack growth during stress corrosion cracking, via full field Digital Image Correlation, is described and data for crack growth development are presented. Intergranular stress corrosion cracks were nucleated in sensitised 304 stainless steel under static uniaxial flexural deflection, within a potassium tetrathionate environment. High resolution optical images of a 2mm by 2mm area are recorded through the test solution during the experiment. The raw images show no observable cracking. However, the high sensitivity of digital image correlation allows small crack opening displacements to be detected. The derived strain map of the sample surface thereby enables imaging of the cracks. Surface cracks with lengths exceeding approximately 30μm can be observed. Post processing of the strain maps is then used to track the development of the cracks.

Intergranular Stress Corrosion Cracking Damage Model: An Approach and Its Development for Alloy 600 in High-Purity Water

CORROSION ◽  
1986 ◽  
Vol 42 (2) ◽  
pp. 99-105 ◽  
Author(s):  
Y. S. Garud ◽  
A. R. McIlree
Keyword(s):  
Strain Rate ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
High Purity ◽  
Corrosion Cracking ◽  
Model Parameters ◽  
Alloy 600 ◽  
Intergranular Stress Corrosion ◽  
Film Rupture ◽  
Intergranular Stress Corrosion Cracking

Abstract A logical approach to quantitative modeling of intergranular stress corrosion cracking (IGSCC) is presented. The approach is based on the supposition (supported partly by experimental and field observations, and by a related plausible underlying mechanism) that strain rate is a key variable. The approach is illustrated for the specific case of NiCrFe Alloy 600 in high-purity water. Model parameters are determined based on the constant stress IGSCC data (between 290 and 365 C) assuming a power law relation between the damage and the nominal strain rate. The model may be interpreted in terms of a film rupture mechanism of the corrosion process. The related mechanistic considerations are examined for the specific case. Resulting calculations and stress as well as temperature dependence are shown to be in good agreement with the data. More data are needed for further verification under specific conditions of interest.

Investigation of IG-SCC growth kinetics in Al-Mg alloys in thin film environments

CORROSION ◽  
10.5006/3833 ◽  
2021 ◽  
Author(s):  
Patrick Steiner ◽  
Zachary Harris ◽  
Carolina Vicente Moraes ◽  
Robert Kelly ◽  
james burns
Keyword(s):  
Thin Film ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Computational Modelling ◽  
Close Correlation ◽  
Open Circuit ◽  
Cathodic Current ◽  
Anodized Aluminum ◽  
Intergranular Stress Corrosion

The effect of thin film environments on the intergranular stress corrosion cracking (IG-SCC) behavior of AA5083-H131 was investigated using fracture mechanics-based testing, high-fidelity monitoring of crack growth, and electrochemical potential measurements. A protocol for conducting thin film IG-SCC fracture mechanics experiments with anodized aluminum oxide (AAO) membranes is developed and the ability to maintain films of specific thicknesses without impeding oxygen diffusion during testing is validated via EIS testing and computational modelling. The IG-SCC susceptibility was found to increase once a critical thin film thickness of 82 µm was achieved; above this thickness a duality in IG-SCC susceptibility behavior was observed. These results are analyzed in the context of a coupled anodic dissolution and hydrogen (H) embrittlement mechanism, where susceptibility is found to scale with the cathodic limitation of the governing IG-SCC mechanism. Specifically, thinner film thicknesses led to limitations on the amount of cathodic current availability, which caused a decrease in the dissolution at the crack tip, a less aggressive crack chemistry development, and thus lower levels of H production. A close correlation between the open circuit potential of the bulk surface and the crack growth kinetics was also observed, consistent with trends reported in previous IG-SCC studies on this alloy.

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