Crack Chemistry Control of Intergranular SCC in Sensitized Al-Mg

Crane, Cortney B.; Kelly, Robert G.; Gangloff, Richard P.

doi:10.5006/1852

Cited by 17 publications

(26 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A complimentary IGSCC model for this particular alloy exposed to marine environment couples this model to include mechanical effects. [23,25,76] Accuracy of the Model The model predicted the trend of increasing IGC depths with exposure time, with the simulated and experimental data for propagation in the L direction ( Figure 16b…”

Section: Relevance Of the Modelmentioning

confidence: 90%

Model to predict intergranular corrosion propagation in three dimensions in AA5083-H131

et al. 2016

View full text Add to dashboard Cite

A three-dimensional (3-D) granular model that has the capability of predicting time-dependent intergranular corrosion (IGC) damage propagation depths in AA5083-H131 exposed to 0.6 M NaCl solution under potential control is presented. The geometry of grains and degree of sensitization (DoS) of grain boundaries were utilized as inputs, organized in a database, which informed the model to produce IGC depth distributions. The dependencies of IGC depth with exposure time, DoS, and orientation of propagation, both in terms of propagation kinetics and damage morphology, are outputs from the model. The model was calibrated by comparing outputted damage depths to IGC depth data from experiments. Model validation was achieved by comparing the predicted to experimental IGC depths based on image analyses of metallographic cross-section of AA5083-H131 exposed under the same conditions. The relevance and limitations of the current version of the model are discussed.

show abstract

Section: Relevance Of the Modelmentioning

confidence: 90%

Model to predict intergranular corrosion propagation in three dimensions in AA5083-H131

et al. 2016

View full text Add to dashboard Cite

show abstract

“…10 , the sensitisation of the AA5083-H131 material plateaus at 30 mg/cm 2 . Two previously published AA5083-H131 100 °C DoS series in the literature exhibit a contradictory plateau of approximately 55 mg/cm 2 21 , 40 . For these reasons, it was found that the JMAK model was very accurate at predicting the relative kinetics of sensitisation but would often be a poor fit for individual series if they exhibited a considerable deviation from the approximate average scaling factors (DoS = 3.2 mg/cm 2 and DoS = 55 mg/cm 2 for zero and full coverage of AA5083-H131, respectively) as seen for the 100 °C DoS series in Fig.…”

Section: Resultsmentioning

confidence: 87%

Experiment-based modelling of grain boundary β-phase (Mg2Al3) evolution during sensitisation of aluminium alloy AA5083

Zhang

Steiner

Agnew

et al. 2017

Sci Rep

View full text Add to dashboard Cite

An empirical model for the evolution of β-phase (Mg2Al3) along grain boundaries in aluminium alloy AA5083 (Al-Mg-Mn) during isothermal exposures is proposed herein. Developing a quantitative understanding of grain boundary precipitation is important to interpreting intergranular corrosion and stress corrosion cracking in this alloy system. To date, complete ab initio models for grain boundary precipitation based upon fundamental principles of thermodynamics and kinetics are not available, despite the critical role that such precipitates play in dictating intergranular corrosion phenomena. Empirical models can therefore serve an important role in advancing the understanding of grain boundary precipitation kinetics, which is an approach applicable beyond the present context. High resolution scanning electron microscopy was to quantify the size and distribution of β-phase precipitates on Ga-embrittled intergranular fracture surfaces of AA5083. The results are compared with the degree of sensitisation (DoS) as judged by nitric acid mass loss testing (ASTM-G67-04), and discussed with models for sensitisation in 5xxx series Al-alloys. The work herein allows sensitisation to be quantified from an unambiguous microstructural perspective.

show abstract

“…8,56 While assumptions on chromium dissolution rates and hydrolysis numerical solutions made exact prediction of crack tip pH difficult, the authors concluded that dissolution and hydrolysis of alloying elements can be important. Indirect evidence of the importance of alloying element hydrolysis in the crack environment has been noted by Crane et al 57 for Al−Mg alloys where MgCl 2 additions to bulk concentrated AlCl 3 crack simulated solutions were made to estimate the impact of Mg dissolution and hydrolysis on crack pH for sensitized high-Mg 5xxx Al alloys. It was found that addition of MgCl 2 decreased bulk solution pH below 1.…”

Section: Prevailing Knowledge Gapsmentioning

confidence: 94%

Chemical and electrochemical conditions within stress corrosion and corrosion fatigue cracks

Bland

Locke

2017

npj Mater Degrad

View full text Add to dashboard Cite

In the area of environment assisted cracking, literature aimed at understanding the chemical and electrochemical conditions at/ near the crack tip establishes that the crack tip is occluded and not well represented by bulk conditions. A review of the relevant literature, both modeling and experimental, is presented here and shows that crack tip conditions are determined by the balance between high metal ion concentrations resulting from crack tip anodic reactions and subsequent hydrolysis, mass transport (including ion migration, diffusion, and advection), and electrochemical polarization of the bold surface, which determines the extent of anodic and cathodic reactions occurring in the crack environment. Under both freely corroding conditions and anodic polarizations, the crack tip pH decreases with increasing polarization above the freely corroding condition, most often leading to a very acidic crack environment. Under sufficient cathodic polarization, the crack tip pH increases. Because of high-anion and -cation concentrations in the crack environment, an IR drop down the crack exists, leaving the crack tip relatively unpolarizable. Ion migration enhances the occluded nature of the crack tip by supplying anions from the bulk solution to maintain electroneutrality at the crack tip. Diffusion to counteract this concentration gradient is minimal and only plays a role in crack tip conditions at very small crack lengths. When cyclic loading conditions are encountered, the occluded nature of the crack tip can be counteracted by advection; although, the role decreases with decreasing f and increasing R, essentially as corrosion fatigue conditions approach those of stress corrosion cracking.npj Materials Degradation (2017) 1:12 ; doi:10.1038/s41529-017-0015-0 INTRODUCTION Structural alloys must withstand both demanding mechanical loads and corrosive environmental conditions when utilized in many applications. Consequently, these materials can be susceptible to premature failure by environment assisted cracking (EAC) when the loading and environmental conditions are sufficiently aggressive. The influence of EAC on the performance and life of structural alloys can be seen in many applications such as oil and gas, nuclear power, nuclear waste storage, and aerospace. For example, several reviews of aircraft structural failures and teardown inspections concluded that fatigue and corrosion dominate aerospace component failures 1, 2 with 78% of the corrosion damage sites identified during teardown having initiated fatigue cracks.2 In addition, the United States Nuclear Regulatory Committee (NRC) released a report in 2014 concluding that one of two top priority needs is understanding stress corrosion cracking (SCC) of spent nuclear fuel storage canisters.

show abstract

Crack Chemistry Control of Intergranular SCC in Sensitized Al-Mg

Cited by 17 publications

References 55 publications

Model to predict intergranular corrosion propagation in three dimensions in AA5083-H131

Model to predict intergranular corrosion propagation in three dimensions in AA5083-H131

Experiment-based modelling of grain boundary β-phase (Mg2Al3) evolution during sensitisation of aluminium alloy AA5083

Chemical and electrochemical conditions within stress corrosion and corrosion fatigue cracks

Contact Info

Product

Resources

About