Investigation on the protective role of local AL cladding against corrosion damage and hydrogen embrittlement of 2024 aluminum alloy specimens

The present investigation aims to inquire whether Al cladding of 2024 aluminum alloy specimens could provide, additionally to the expected protection against corrosion damage, also a protection against the corrosion induced hydrogen embrittlement of the alloy. The latter is observed when bare 2024 material is subjected to laboratory exfoliation corrosion exposure in the absence of mechanical loading. The study aims also to ponder on the question whether local Al cladding at small regions of the specimen surface might suffice for protecting the specimen against corrosion damage and hydrogen embrittlement. The work comprises the results of an extensive experimental investigation including tensile tests on precorroded 2024 specimens protected through both complete and local surface Al cladding, metallographic and fractographic analyses as well as measurements of the hydrogen up take during the corrosion process

Effect of prior deformation and heat treatment on the corrosion-induced hydrogen trapping in aluminium alloy 2024

The nature of the corrosion-induced hydrogen trapping in Al-alloy 2024-T351 was studied by thermal desorption spectroscopy. The microstructure was altered by solution treatment and plastic deformation, prior to corrosion. The results showed that the high temperature, 500. °C, trap state (T4 state) is associated with the S-phase. In the absence of S-phase, hydrogen is trapped at vacancies, which liberate hydrogen at higher temperatures. Plastic deformation prior to corrosion revealed that the trap state at 400. °C (T3 state) is associated with dislocations. High plastic strains (above 0.06) lead to a reduction of hydrogen trapped in both dislocations and the S-phase. © 2013 Elsevier Ltd

Analysis of the effects of exfoliation corrosion on the fatigue behaviour of the 2024-T351 aluminium alloy using the fatigue damage map

The concept of the Fatigue Damage Map (FDM) is implemented to quantify the effects of exfoliation corrosion damage on the fatigue behaviour of the 2024-T351 aluminium alloy. This is achieved by using extensive experimental data involving tensile, fracture toughness, fatigue as well as fatigue crack growth tests on pre-exfoliated 2024-T351 specimens. The analysis suggests that exfoliation exposure leads to an increase in accelerated crack growth stage (Stage III) at the expense of Stage II (long crack growth). It also suggests that the transition from Stage I crack growth (short crack) to Stage II for the same stress level occurs at smaller crack lengths for the exfoliated material. Furthermore, stress intensity range values for onset of crack growth rate acceleration (Stage III) obtained from the experimental results for the pre-corroded specimens are in accordance with the results of the FDM analysis. The outcome of the analysis, demonstrates that the a priori negligence of the corrosion effect in structural integrity analyses of aged aircraft components may lead to significant overestimation of the damage tolerance ability of the structure. © 2005 Elsevier Ltd. All rights reserved

Evidence on the corrosion-induced hydrogen embrittlement of the 2024 aluminium alloy

The present work aims to provide evidence of corrosion-induced hydrogen embrittlement of the aircraft aluminium alloy 2024. An extensive experimental investigation involving metallographic and fractographic analyses as well as mechanical testing was performed. The corrosion exposure led to a moderate reduction in yield and ultimate tensile stress and a dramatic reduction in tensile ductility. Metallographic investigation of the specimens revealed a hydrogen-rich embrittled zone just below the corrosion layer. Furthermore, fractographic analyses showed an intergranular fracture at the specimen surface followed by a zone of quasi-cleavage fracture and further below an entirely ductile fracture. Mechanical removal of the corroded layers restored the yield and ultimate stress almost to their initial values but not the tensile ductility. The tensile ductility was restored to the level of the uncorroded material only after heat treatment at 495 degrees C. Measurement of hydrogen evolution with temperature showed that by heating the corroded alloy at 495 degrees C, the trapped hydrogen is released