PSI - Issue 68

R.J. Mostert et al. / Procedia Structural Integrity 68 (2025) 351–357 R.J. Mostert et al. / Structural Integrity Procedia 00 (2025) 000–000

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• The damaged grain boundaries provide a pathway for hydrogen diffusion into the matrix, where it results in the embrittlement of the bulk of the alloy. The bulk embrittlement is experienced as a reduction of the plastic deformation capability of the alloys, as observed in the reduction of the percentage of elongation to fracture following EXCO exposure. • Pre-stretching of these alloys result in a degradation of tensile and fracture toughness properties, as determined at slow strain rates. It furthermore leads to an increase in the shallow surface crack density. • A relatively low pre-stretching level of 1.5 % for AA2198-T8, leads to a maximum regarding both the shallow surface crack density and the extent of the corrosion-induced tensile property degradation. This correlation is believed to be due to the increased number of pathways provided for hydrogen diffusion for this case, through the increase of the number of degraded grain boundaries. Acknowledgement This research has been financed by the Hellenic Foundation for Research and Innovation, under the 2 nd Call for H.F.R.I. Research Projects to support Faculty Members and Researchers (Proposal ID: 03385, MIS Acronym: CorLi, Title: Corrosion susceptibility, degradation and protection of advanced Al-Li aluminium alloys). The financial support of Mr Pretorius by the Advanced Metals Initiative of the South African Department of Science and Innovation, is gratefully acknowledged. References ASTM E8M, 2016. Standard Test Method for Tension Testing of Metallic Materials, ASTM International, West Conshohocken, PA. ASTM E561, 2019. Standard Test Method for KR curve determination, ASTM International, West Conshohocken, PA. ASTM G34, 2001. Standard Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys (EXCO Test), ASTM International, West Conshohocken, PA. Charalampidou, C-M, Pretorius, C.C.E., Salojee, M, Karousos, D, Khodja, M., Mostert, R.J, † Alexopoulos N.D., 2024. Investigation of the mechanisms affecting corrosion susceptibility of wrought aeronautical aluminium alloys Al-Cu-Li (AA2198) and Al-Cu (AA2024) for different pre-stretching levels. Journal of Materials Research and Technology (In review). Pretorius, C.C.E, 2024. The Role of Hydrogen in the Surface and Bulk Embrittlement of the Tensile Properties and Crack Extension Resistance behaviour of High-Strength Aluminium Alloy 2024, Master’s Dissertation, University of Pretoria, South Africa. Pretorius, C.C.E, Mostert, R.J, Charalampidou, C-M, Alexopoulos N.D., 2024. The role of hydrogen in the corrosion-induced reduction of plane stress fracture toughness and strain-induced intergranular cracking of AA2024. Structural Integrity Procedia 54, 617 – 625. Pretorius, C.C.E., Mostert, R.J, Ramjee, S., 2021. The crack growth resistance behaviour of aluminium alloy 2024-T3 at slow strain rates after exposure to standard corrosive environments. ‡ Journal of SAIMM 121, 151 – 158.