Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading

Ma, Tian-Hao; Wang, Yu-Xin; Chang, Le; Zhang, Wei; Zhao, Jian-Ping; Zhou, Chang-Yu

doi:10.3390/ma18225122

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Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading

by

Tian-Hao Ma

,

Yu-Xin Wang

,

Le Chang

,

Wei Zhang

,

Jian-Ping Zhao

and

Chang-Yu Zhou

^*

School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China

^*

Author to whom correspondence should be addressed.

Materials 2025, 18(22), 5122; https://doi.org/10.3390/ma18225122

Submission received: 29 September 2025 / Revised: 29 October 2025 / Accepted: 10 November 2025 / Published: 11 November 2025

(This article belongs to the Special Issue Mechanical Behavior and Multiscale Modeling of Advanced Structural Materials)

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Abstract

Multiaxial low-cycle fatigue (MLCF) behavior of laser powder bed fused (L-PBF) Ti-6Al-4V was systematically investigated with four building direction (BD) in this paper. Proportional and non-proportional strain-controlled MLCF tests characterized cyclic softening and fracture mechanisms. L-PBF Ti-6Al-4V exhibits three-stage cyclic softening with occasional initial hardening, while non-proportional softening predominates, contrasting with conventional titanium alloys. Macro-micro characterization reveals that defect density and cleavage morphology strongly influence fatigue performance across BD. Fatigue life was predicted using analytical models (FS and KBMP) and a hybrid physics- and data-driven VAE-ANN model. While the KBMP model improves predictions over FS, both fail to fully account for BD effects. Incorporating macro-micro features, the VAE-ANN model achieves highly accurate MLCF life predictions within 10% error. These results highlight the critical roles of BD and microstructural characteristics in governing the MLCF behavior of L-PBF Ti-6Al-4V.

Keywords: multiaxial fatigue; laser powder bed fusion; Ti-6Al-4V; critical plane; artificial neural network

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MDPI and ACS Style

Ma, T.-H.; Wang, Y.-X.; Chang, L.; Zhang, W.; Zhao, J.-P.; Zhou, C.-Y. Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading. Materials 2025, 18, 5122. https://doi.org/10.3390/ma18225122

AMA Style

Ma T-H, Wang Y-X, Chang L, Zhang W, Zhao J-P, Zhou C-Y. Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading. Materials. 2025; 18(22):5122. https://doi.org/10.3390/ma18225122

Chicago/Turabian Style

Ma, Tian-Hao, Yu-Xin Wang, Le Chang, Wei Zhang, Jian-Ping Zhao, and Chang-Yu Zhou. 2025. "Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading" Materials 18, no. 22: 5122. https://doi.org/10.3390/ma18225122

APA Style

Ma, T.-H., Wang, Y.-X., Chang, L., Zhang, W., Zhao, J.-P., & Zhou, C.-Y. (2025). Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading. Materials, 18(22), 5122. https://doi.org/10.3390/ma18225122

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Fatigue Behavior and Life Prediction of L-PBF Ti64 with Critical Plane Based Small Building Direction Variations Under Non-Proportional and Multiaxial Loading

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