PSI - Issue 68

ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 68 (2025) 351–357

European Conference on Fracture 2024 On the mechanisms for surface and bulk embrittlement of AA2024 and AA2198 aluminium alloys, following hydrogen exposure R.J. Mostert a, * , C.C.E. Pretorius a, , C-M Charalampidou b , N. Alexopoulos b a University of Pretoria, Department of Materials Science and Metallurgical Engineering, Lynnwood Road, Hatfield, Pretoria 0002, South Africa. b Research Unit of Advanced Materials, Department of Financial Engineering, School of Engineering, University of the Aegean, 41 Kountouriοtou str., Chios 82132, Greece. Abstract In order to investigate the mechanism of embrittlement of two high-strength aluminium alloys, AA2024-T3 and AA2198-T8, a number of tensile and compact tension specimens were subjected to two hours of immersion in an exfoliation corrosion (EXCO) solution. Some of these samples had previously been subjected to different levels of pre-stretching, before immersion. It was found that, for the Al-Cu-Li alloy AA2198, a maximum of tensile embrittlement was observed at a low pre-stretching level of 1.5 %. At this level, a maximum was also observed with regard to the surface crack density observed, following testing. The surface cracking was shallow and intergranular, but the primary fracture surfaces were found to be ductile with multi-void coalescence. Scanning electron microscopy work demonstrated that, following EXCO exposure, a thin (~ 100 µm) subsurface layer of intergranular attack was present. A degassing heat treatment significantly reduced the diffusible hydrogen, but the intergranular surface cracking remained. A mechanism is proposed to explain the embrittlement observed both on the surfaces and in the bulk of the alloys. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Aluminium Alloy 2198; Aluminium Alloy 2024; EXCO exposure; hydrogen embrittlement; intergranular corrosion; diffusable hydrogen European Conference on Fracture 2024 On the mechanisms for surface and bulk embrittlement of AA2024 and AA2198 aluminium alloys, following hydrogen exposure R.J. Mostert a, * , C.C.E. Pretorius a, , C-M Charalampidou b , N. Alexopoulos b a University of Pretoria, Department of Materials Science and Metallurgical Engineering, Lynnwood Road, Hatfield, Pretoria 0002, South Africa. b Research Unit of Advanced Materials, Department of Financial Engineering, School of Engineering, University of the Aegean, 41 Kountouriοtou str., Chios 82132, Greece. Abstract In order to investigate the mechanism of embrittlement of two high-strength aluminium alloys, AA2024-T3 and AA2198-T8, a number of tensile and compact tension specimens were subjected to two hours of immersion in an exfoliation corrosion (EXCO) solution. Some of these samples had previously been subjected to different levels of pre-stretching, before immersion. It was found that, for the Al-Cu-Li alloy AA2198, a maximum of tensile embrittlement was observed at a low pre-stretching level of 1.5 %. At this level, a maximum was also observed with regard to the surface crack density observed, following testing. The surface cracking was shallow and intergranular, but the primary fracture surfaces were found to be ductile with multi-void coalescence. Scanning electron microscopy work demonstrated that, following EXCO exposure, a thin (~ 100 µm) subsurface layer of intergranular attack was present. A degassing heat treatment significantly reduced the diffusible hydrogen, but the intergranular surface cracking remained. A mechanism is proposed to explain the embrittlement observed both on the surfaces and in the bulk of the alloys. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Aluminium Alloy 2198; Aluminium Alloy 2024; EXCO exposure; hydrogen embrittlement; intergranular corrosion; diffusable hydrogen © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

* Corresponding author. Tel.: +27-82-464-1995 e-mail address: roelf.mostert@up.ac.za * Corresponding author. Tel.: +27-82-464-1995 e-mail address: roelf.mostert@up.ac.za

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.065