Understanding Fatigue Properties of Additively Manufactured Ti-6Al-4V
We investigate additively manufactured titanium alloys regarding their fatigue properties. Here we find a correlation between the fatigue properties based on microstructure, surface and internal quality. We propose a novel methodology, what we call MIS -Microstructure, Integrity, Surface-, to describe failing parts according to their surface and internal quality. The method delivers correction factors for end users to assess the fatigue strength in the stress-life domain while noting the application limits.
Additive manufacturing (AM) of Ti-6Al-4V parts offers mechanical properties superior to cast and wrought materials, but uncertainties remain regarding their fatigue performance. This study reviews the fatigue behavior of AM-produced Ti-6Al-4V, focusing on the interplay of microstructure, internal defects, and surface quality.
The researchers introduced the MIS (Microstructure, Internal, Surface) model to describe the hierarchical failure mechanisms of AM parts. The model emphasizes that fatigue performance depends on reducing surface roughness and internal defect sizes to critical thresholds. By doing so, the material can transition to a microstructure-dominated failure domain, improving its fatigue strength.
Key findings include:
Fatigue Strength Analysis: Two reference S-N curves were developed—one for surface-initiated cracks and another for cracks originating from internal defects. Correction factors were proposed for these curves to quantify fatigue performance.
Surface and Internal Quality: Surface treatment and minimizing internal defect sizes significantly influence fatigue resistance. If the surface cannot be improved, failure will be governed by the surface domain alone.
Microstructure Dominance: With optimal surface and internal quality, the microstructure becomes the governing factor in fatigue resistance.
While this study provides a framework for understanding fatigue in AM Ti-6Al-4V parts, the authors note that more research is needed. Factors like residual stress, size effects, and loading conditions require further investigation to refine the MIS model and fully understand the mechanisms behind fatigue performance in AM materials.
This paper serves as a foundational guide for researchers aiming to optimize the fatigue properties of AM Ti-6Al-4V alloys.
If you use our data please cite as : @article{johnsen2024factors, title={Factors affecting the fatigue strength of additively manufactured Ti-6Al-4V parts}, author={Johnsen, Anders Rygg and Petersen, Jan Erik and Pedersen, Mikkel Melters and Y{\i}ld{\i}r{\i}m, Halid Can}, journal={Welding in the World}, volume={68}, number={2}, pages={361--409}, year={2024}, publisher={Springer} }
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