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) 131–137

8th International Conference on Structural Integrity and Durability (ICSID2025) High-cycle and very-high-cycle fatigue behaviors of additively manufactured vs. conventional titanium alloys: Microstructural and mechanical insights Hang Su a , Xiangnan Pan b, *, Xu Long c, *, Guian Qian b , Youshi Hong b, *

a Department of Civil Engineering, University of California, Los Angeles, CA 90095, USA b LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China c School of Mechanics and Transportation Engineering, Northwestern Polytechnical University, Xi'an 710129, China

© 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 This study presents a comparative investigation on the high-cycle and very-high-cycle fatigue (HCF–VHCF) behaviors of additively manufactured (AM) and conventionally processed (CP) titanium alloys under fully reversed loading ( R = –1). Emphasis is placed on clarifying how microstructure and defect characteristics jointly govern the transition between microstructure-sensitive and defect-dominated fatigue mechanisms. The AM Ti-6Al-4V alloy, possessing a lamellar martensitic structure and void-type defects such as lack-of-fusion (LoF) pores and gas porosity, exhibits a duplex S–N curve and internal origin fractures with smooth fine granular areas (FGAs) and fish-eye (FiE) morphologies. In contrast, the CP alloy with an equiaxed α+β microstructure shows a nearly linear S–N relation, surface or α/β interface crack initiation, and irregular FGAs, indicating a microstructure-controlled fatigue process. Micro- and nano-structural observations indicate the formation of nanoscale grains within the crack-initiation zone, suggesting a universal mechanism of cyclic plastic refinement in the VHCF regime. The results provide mechanistic insights into the distinct fatigue responses of AM and CP titanium alloys and underscore the importance of defect morphology control and microstructural design in improving the long-life reliability of AM components. © 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: very-high-cycle fatigue (VHCF); S-N curve; fractography; additive manufacturing (AM); titanium alloy

* Corresponding authors. E-mail address: panxiangnan@lnm.imech.ac.cn (X.P.), xulong@nwpu.edu.cn (X.L.), hongys@imech.ac.cn (Y.H.)

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.2026.04.021