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Proportional Multiaxial Fatigue Behavior and Life Prediction of Laser Powder Bed Fusion Ti-6Al-4V with Critical
Tian-Hao Ma1, Yu-Xin Wang1, Wei Zhang1
1School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China.
Materials (Basel, Switzerland)
|November 13, 2025
Summary
This study investigated the multiaxial low-cycle fatigue (MLCF) of laser powder bed fusion Ti-6Al-4V (Ti64) components. A new KBMP-λ model accurately predicts fatigue life within 20% error for complex designs.
Area of Science:
- Materials Science
- Mechanical Engineering
- Additive Manufacturing
Background:
- Laser Powder Bed Fusion (L-PBF) enables complex geometries, overcoming conventional manufacturing limits.
- Ti-6Al-4V (Ti64) is a critical alloy in aerospace and biomedical applications.
- Understanding fatigue behavior in L-PBF Ti64 is crucial for structural integrity.
Purpose of the Study:
- To evaluate the multiaxial low-cycle fatigue (MLCF) performance of L-PBF Ti64.
- To investigate cyclic softening, mean stress, and fracture mechanisms.
- To develop and validate a fatigue life prediction model.
Main Methods:
- MLCF tests on L-PBF Ti64 specimens in four build orientations.
- Proportional strain-controlled loading.
- Microscopic analysis of fracture surfaces.
- Development of the KBMP-λ life prediction model.
Main Results:
- L-PBF Ti64 exhibited three-stage cyclic softening.
- Fatigue cracks initiated from internal lack-of-fusion defects.
- Crack propagation showed cleavage and quasi-cleavage features.
- The KBMP-λ model achieved high accuracy (within 20% error).
Conclusions:
- L-PBF Ti64 demonstrates distinct fatigue softening behavior.
- Internal defects significantly influence fatigue crack initiation.
- The KBMP-λ model provides a reliable tool for designing L-PBF titanium components under multiaxial fatigue loading.
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