PSI - Issue 68

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 68 (2025) 1051–1058 Structural Integrity Procedia 00 (2025) 000–000

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European Conference on Fracture 2024 Effect of Hydrogen on Plasticity in Advanced High-Strength Steels Used in Automotive Applications Adam Ståhlkrantz a *, Birhan Sefer a , Tuomo Nyyssönen a , Olli Oja b European Conference on Fracture 2024 Effect of Hydrogen on Plasticity in Advanced High-Strength Steels Used in Automotive Applications Adam Ståhlkrantz a *, Birhan Sefer a , Tuomo Nyyssönen a , Olli Oja b a Swerim AB, Stockholm, Sweden b SSAB, Hämeenlinna, Finland Abstract This work studied the influence of hydrogen trapped in retained austenite on the mechanical properties of advanced high strength steel (AHSS) in tensile testing. It was found that hydrogen affected both the true strain at necking as well as the true fracture strain, when compared to a non-charged specimen. Moreover, when testing specimens with varying amounts of retained austenite, the drop in true strain at necking was in correlation to the amount of retained austenite present in the AHSS, while no such correlation was present for true fracture strain. The results from this work indicate that while trapping of hydrogen is usually seen as a positive mitigating mechanism of hydrogen embrittlement, for steels with retained austenite it may severely limit the capability for strain hardening. This could have severe consequences, for example, for a shock-absorbing crash box component in an automotive. Keywords: Retained austenite; Hydrogen; AHSS; Local formability 1. Introduction The increased use of hydrogen in industry and the transition to a hydrogen-based economy have raised the need to better understand the hydrogen/metal interactions in advanced high-strength steels (AHSS). This is because the origin of many failures in hydrogen-centric applications is related to hydrogen in the form of hydrogen delayed cracking (HDC), hydrogen induced cracking (HIC) or hydrogen embrittlement (HE). All these phenomena occur when the metal is exposed to hydrogen containing environments and atomic hydrogen has been absorbed. The absorbed atomic hydrogen deteriorates important properties such as fracture toughness, ductility and fatigue resistance. Therefore, in © 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 a Swerim AB, Stockholm, Sweden b SSAB, Hämeenlinna, Finland Abstract This work studied the influence of hydrogen trapped in retained austenite on the mechanical properties of advanced high strength steel (AHSS) in tensile testing. It was found that hydrogen affected both the true strain at necking as well as the true fracture strain, when compared to a non-charged specimen. Moreover, when testing specimens with varying amounts of retained austenite, the drop in true strain at necking was in correlation to the amount of retained austenite present in the AHSS, while no such correlation was present for true fracture strain. The results from this work indicate that while trapping of hydrogen is usually seen as a positive mitigating mechanism of hydrogen embrittlement, for steels with retained austenite it may severely limit the capability for strain hardening. This could have severe consequences, for example, for a shock-absorbing crash box component in an automotive. Keywords: Retained austenite; Hydrogen; AHSS; Local formability 1. Introduction The increased use of hydrogen in industry and the transition to a hydrogen-based economy have raised the need to better understand the hydrogen/metal interactions in advanced high-strength steels (AHSS). This is because the origin of many failures in hydrogen-centric applications is related to hydrogen in the form of hydrogen delayed cracking (HDC), hydrogen induced cracking (HIC) or hydrogen embrittlement (HE). All these phenomena occur when the metal is exposed to hydrogen containing environments and atomic hydrogen has been absorbed. The absorbed atomic hydrogen deteriorates important properties such as fracture toughness, ductility and fatigue resistance. Therefore, in

* Corresponding author. Tel.: +46761451441 E-mail address: adam.stahlkrantz@swerim.se

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.2025.06.169 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 * Corresponding author. Tel.: +46761451441 E-mail address: adam.stahlkrantz@swerim.se