PSI - Issue 82

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2026) 000–000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 82 (2026) 119–124

© 2026 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 ICSID organizers Abstract The alpha-case layer in titanium alloys forms due to titanium's high affinity for oxygen, which increases with temperature. Above 500°C, Ti 3 O, Ti 2 O, and Ti 3 O 2 oxides form on the alloy surface depending on the wt.% of oxygen in the atmosphere (more than 15 wt.%). To investigate the effect of isothermal temperature dwell on the alpha-case layer thickness, the alloy was heated to a temperature above the β transus of 1050°C with dwell times of 0.5, 1, and 1.5 hours. The average thickness of the formed alpha-case layer ranged from 122.5 µm (0.5 hours) to 266.7 µm (1.5 hours). The fatigue tests were carried out through three-point bending with a cycle asymmetry parameter R < 1, a loading frequency of f = 60÷70 Hz, a mean stress σ m = 311 MPa, and a loading amplitude σ a = 155.5 MPa÷272 MPa. In general, the fatigue life of the alloy with the alpha-case layer is unpredictable due to the occurrence of fine or significant cracks in that surface layer, which significantly influence the initiation and growth of fatigue cracks and, hence, the number of cycles to failure. © 2026 The Authors. Copy from the contract: 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 ICSID organizers Keywords: alpha-case layer; Ti6Al4V alloy; b -transus annealing; fatigue life; SEM analysis a 8th International Conference on Structural Integrity and Durability (ICSID2025) Formation of the alpha-case layer and its influence on the fatigue crack propagation of beta annealed Ti6Al4V alloy Juraj Belan a, *, Milan Uhríčik a , Lenka Markovičová a , Silvia Hudecová a , Veronika Chvalníková a a University of Žilina, Faculty of Mechanical Engineering, Department of Materials Science, Univerzitná 8215/1, Žilina 01026, Slovakia a

1. Introduction Titanium and its alloys have a high affinity for oxygen. This increases with rising temperatures. It is a well-known

* Corresponding author. Tel.: +421-41-513-2631. E-mail address: juraj.belan@fstroj.uniza.sk

2452-3216 © 2026 The Authors. Copy from the contract: 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 ICSID organizers

2452-3216 © 2026 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 ICSID organizers 10.1016/j.prostr.2026.04.019