PSI - Issue 66

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

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 66 (2024) 87–101

8th International Conference on Crack Paths Investigating the fatigue fracture mechanisms of laser powder bed fusion produced Ti-6Al-4V Nur Mohamed Dhansay a *, Kim Vanmeensel b , Thorsten Hermann Becker c a Stellenbosch University, Department of Mechanical and Mechatronics Engineering, Stellenbosch Central, Stellenbosch 7599, South Africa b KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg, Leuven 3001, Belgium c University of Cape Town, Department of Mechnical Engineering, Rondebosch, Cape Town 7700, South Africa Abstract Laser powder bed fusion (LPBF) produced Ti-6Al-4V often has large residual stresses, brittle martensitic microstructure, porosity and anisotropic behaviour. This typically results in poor fatigue behaviour. However, the insight into what the specific fatigue fracture mechanisms are, which causes poor fatigue properties, are limited. This study investigated the near-threshold FCGRs of LPBF produced Ti-6Al-4V. It was found that when the load-reduction technique was applied for obtaining near-threshold FCGRs, the anisotropic behaviour could be linked to the residual stresses, prior beta grain morphology and their relation to crack closure effects. For the bi-modal condition, the improvement in comparison to the as-fabricated and stress relieved conditions has been linked to increase in grain size and the presence of β phase. Anisotropic effects manifested themselves more distinctly in the global “closure-affected” region due to roughness-induced crack closure. Whereas intrinsic behaviour is more distinctly observed in the global “closure-free” region where microstructural plastic flow and energy dispersion are the main mechanisms in effect. © 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 CP 2024 Organizers Keywords: Near-threshold; fatigue; crack-closure; laser powder bed fusion © 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 CP 2024 Organizers

* Corresponding author. Tel.: +27-21-808-4045 E-mail address: nurmdhansay@sun.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 CP 2024 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 CP 2024 Organizers 10.1016/j.prostr.2024.11.058