CHARACTERISATION OF THE MICROSTRUCTURE AND DEFECTS DURING THE DIRECT ENERGY DEPOSITION OF HYBRID Ti6Al4V IN A LOW-QUALITY ATMOSPHERE
Abstract
Additive manufacturing is a complicated process, including powder preparation and post-processing. The atmosphere during the processing of sensitive alloys like Ti6Al4V is among the most important factors. The N content influences the mechanical properties in a significant way. Therefore, it is essential to understand, recognise, and identify the problems in case of machine malfunction or human error. The influence of a low-quality atmosphere on the microstructure evolution and mechanical properties was investigated during the direct energy deposition of hybrid additive-manufactured Ti6Al4V. The properties of the built parts were characterised by chemical analyses, light and electron microscopy, and mechanical testing. High concentrations of N, which absorbed and dissolved with every deposition layer of the direct-energy-deposition process, promoted the formation of a layer of α-scale on the part’s surface. The presence of α-scale was confirmed by observing the sample surfaces and the lack of fusion pores where a layer of α-scale remained. The α-scale partially or entirely dissolved during the next deposition layer. The morphology of the partially melted, α-scale depended on the size of the deposition and, thus, on the temperature evolution during the direct energy deposition.
References
2. Pauzon, C.; Hryha, E.; Forêt, P.; Nyborg, L. Effect of Argon and Nitrogen Atmospheres on the Properties of Stainless Steel 316 L Parts Produced by Laser-Powder Bed Fusion. Mater Des., (2019), 179, 107873, doi:10.1016/J.MATDES.2019.107873
3. Khorasani, A.; Gibson, I.; Kozhuthala Veetil, J.; Amir, &; Ghasemi, H. A Review of Technological Improvements in Laser-Based Powder Bed Fusion of Metal Printers, The International Journal of Advanced Manufacturing Technology, (2020), 108, 191–209, doi:10.1007/s00170-020-05361-3
4. Bermingham, M.J.; Thomson-Larkins, J.; St John, D.H.; Dargusch, M.S. Sensitivity of Ti-6Al-4V Components to Oxidation during out of Chamber Wire + Arc Additive Manufacturing. J Mater Process Technol., (2018), 258, 29–37, doi:10.1016/J.JMATPROTEC.2018.03.014
5. Gushchina, M.O.; Kuzminova, Y.O.; Kudryavtsev, E.A.; Babkin, K.D.; Andreeva, V.D.; Evlashin, S.A.; Zemlyakov, E. V. Effect of Scanning Strategy on Mechanical Properties of Ti-6Al-4V Alloy Manufactured by Laser Direct Energy Deposition. J Mater Eng Perform., (2022), 31, 2783–2791, doi:10.1007/S11665-021-06407-7
6. C. Leyens, M. Peters, Titanium and Titanium Alloys: Fundamentals and Applications, Wiley‐VCH Verlag GmbH & Co. KGaA, 2003. doi:10.1002/3527602119
7. Conrad, H. Effect of Interstitial Solutes on the Strength and Ductility of Titanium. Prog Mater Sci., (1981), 26, 123–403, doi:10.1016/0079-6425(81)90001-3
8. Du, Y.; Chang, Y.A.; Huang, B.; Gong, W.; Jin, Z.; Xu, H.; Yuan, Z.; Liu, Y.; He, Y.; Xie, F.-Y. Diffusion Coefficients of Some Solutes in Fcc and Liquid Al: Critical Evaluation and Correlation. Materials Science and Engineering: A, (2003), 363, 140–151, doi:10.1016/S0921-5093(03)00624-5
9. Cen, M.-J.; Liu, Y.; Chen, X.; Zhang, H.-W.; Li, Y.-X. Special Report Inclusions in Melting Process of Titanium and Titanium Alloys, CHINA FOUNDRY, (2019), l, 16, doi:10.1007/s41230-019-9046-1
10. Gaddam, R.; Sefer, B.; Pederson, R.; Antti, M.L. Study of Alpha-Case Depth in Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V. IOP Conf Ser Mater Sci Eng., (2013), 48, 012002, doi:10.1088/1757-899X/48/1/012002
11. Godec, M.; Malej, S.; Feizpour, D.; Donik; Balažic, M.; Klobčar, D.; Pambaguian, L.; Conradi, M.; Kocijan, A. Hybrid Additive Manufacturing of Inconel 718 for Future Space Applications. Mater Charact., (2021), 172, 110842, doi:10.1016/J.MATCHAR.2020.110842
12. American Society for Testing and Materials ASTM B348/B348M-19: Standard Specification for Titanium and Titanium Alloy Bars and Billets. In Annual Book of ASTM Standards; (2019); p. 9.
13. Diamanti, M. V.; Del Curto, B.; Pedeferri, M. Interference Colors of Thin Oxide Layers on Titanium. Color Res Appl., (2008), 33, 221–228, doi:10.1002/col.20403.
14. Yilbas, B.S.; Sahin, A.Z.; Al-Garni, A.Z.; Said, S.A.M.; Ahmed, Z.; Abdulaleem, B.J.; Sami, M. Plasma Nitriding of Ti-6Al-4V Alloy to Improve Some Tribological Properties. Surf Coat Technol, (1996), 80, 287–292, doi:10.1016/0257-8972(95)02472-7
15. Bellot, J.P.; Foster, B.; Hans, S.; Hess, E.; Ablitzer, D.; Mitchell, A. Dissolution of Hard-Alpha Inclusions in Liquid Titanium Alloys. Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, (1997), 28, 1001–1010, doi:10.1007/S11663-997-0054-Y/METRICS
16. Mitchell, A. The Electron Beam Melting and Refining of Titanium Alloys. Materials Science and Engineering: A, (1999), 263, 217–223, doi:10.1016/S0921-5093(98)01177-0
