Low-Cycle Fatigue Behavior of Wire and Arc Additively Manufactured Ti-6Al-4V Material

Sebastian Springer, Martin Leitner, Thomas Gruber, Bernd Oberwinkler, Michael Lasnik, Florian Grün

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


Additive manufacturing (AM) techniques, such as wire arc additive manufacturing (WAAM), offer unique advantages in producing large, complex structures with reduced lead time and material waste. However, their application in fatigue-critical applications requires a thorough understanding of the material properties and behavior. Due to the layered nature of the manufacturing process, WAAM structures have different microstructures and mechanical properties compared to their substrate counterparts. This study investigated the mechanical behavior and fatigue performance of Ti-6Al-4V fabricated using WAAM compared to the substrate material. Tensile and low-cycle fatigue (LCF) tests were conducted on both materials, and the microstructure was analyzed using optical microscopy and scanning electron microscopy (SEM). The results showed that the WAAM material has a coarser and more heterogeneous grain structure, an increased amount of defects, and lower ultimate tensile strength and smaller elongation at fracture. Furthermore, strain-controlled LCF tests revealed a lower fatigue strength of the WAAM material compared to the substrate, with crack initiation occurring at pores in the specimen rather than microstructural features. Experimental data were used to fit the Ramberg–Osgood model for cyclic deformation behavior and the Manson–Coffin–Basquin model for strain-life curves. The fitted models were subsequently used to compare the two material conditions with other AM processes. In general, the quasi-static properties of WAAM material were found to be lower than those of powder-based processes like selective laser melting or electron beam melting due to smaller cooling rates within the WAAM process. Finally, two simplified estimation models for the strain-life relationship were compared to the experimentally fitted Manson–Coffin–Basquin parameters. The results showed that the simple “universal material law” is applicable and can be used for a quick and simple estimation of the material behavior in cyclic loading conditions. Overall, this study highlights the importance of understanding the mechanical behavior and fatigue performance of WAAM structures compared to their substrate counterparts, as well as the need for further research to improve the understanding of the effects of WAAM process parameters on the mechanical properties and fatigue performance of the fabricated structures.
Fachzeitschrift Materials
PublikationsstatusVeröffentlicht - 5 Sept. 2023

Bibliographische Notiz

Funding Information:
Special thanks are given to the Austrian Research Promotion Agency (FFG; project number 32765288), who funded the research project with funds of the Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology (bmk) and the Federal Ministry for Digital and Economic Affairs (bmdw).

Publisher Copyright:
© 2023 by the authors.

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