Springer Sebastian, Leitner Martin, Gruber Thomas, Oberwinkler Bernd, Lasnik Michael, Grün Florian
Chair of Mechanical Engineering, Montanuniversität Leoben, 8700 Leoben, Austria.
Voestalpine BÖHLER Aerospace GmbH & Co KG, 8605 Kapfenberg, Austria.
Materials (Basel). 2023 Sep 5;16(18):6083. doi: 10.3390/ma16186083.
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.
增材制造（AM）技术，如电弧增材制造（WAAM），在生产大型复杂结构方面具有独特优势，可缩短交货时间并减少材料浪费。然而，它们在对疲劳性能要求严格的应用中需要对材料性能和行为有透彻的了解。由于制造过程的分层性质，与基体材料相比，WAAM结构具有不同的微观结构和力学性能。本研究调查了与基体材料相比，采用WAAM制造的Ti-6Al-4V的力学行为和疲劳性能。对两种材料都进行了拉伸和低周疲劳（LCF）试验，并使用光学显微镜和扫描电子显微镜（SEM）分析了微观结构。结果表明，WAAM材料具有更粗大且更不均匀的晶粒结构、更多的缺陷数量、更低的极限抗拉强度以及更小的断裂伸长率。此外，应变控制的LCF试验表明，与基体相比，WAAM材料的疲劳强度更低，裂纹起始于试样中的孔隙而非微观结构特征。实验数据用于拟合循环变形行为的Ramberg-Osgood模型和应变寿命曲线的Manson-Coffin-Basquin模型。随后，使用拟合模型将两种材料状态与其他增材制造工艺进行比较。总体而言，由于WAAM工艺中冷却速率较小，发现WAAM材料的准静态性能低于选择性激光熔化或电子束熔化等粉末基工艺。最后，将两种简化的应变寿命关系估计模型与实验拟合的Manson-Coffin-Basquin参数进行了比较。结果表明，简单的“通用材料定律”适用，可用于快速简单地估计循环加载条件下的材料行为。总的来说，本研究强调了了解WAAM结构与其基体材料相比的力学行为和疲劳性能的重要性，以及进一步研究以更好地理解WAAM工艺参数对制造结构的力学性能和疲劳性能影响的必要性。
