Structure and mechanical properties of Ti2AlNb-based alloy welded joints using keyhole plasma arc welding with subsequent heat treatment

Using keyhole plasma arc welding, welded joints of a Ti₂AlNb-based alloy, VTI-4, were obtained, and their structure and mechanical properties were studied. It has been established that the dynamic effect of a keyhole arc had a positive effect on the quality of the welded joint; namely, lack of penetration, porosity, and microcracks were eliminated. The welded joint consisted of a fusion zone (FZ), a heat-affected zone (HAZ), and a base metal (BM). Depending on the phase composition and morphology of the obtained phases, the HAZ can be divided into four zones: HAZ1 with large β-phase grains near the melting line, HAZ2 with large β-phase grains + α₂, HAZ3 with more fragmented β-phase grains retaining more α₂-phase, and HAZ4 with the phase composition β + α₂ + O. Subsequent heat treatment (HT: quenching at 920 °C for 2 h, cooling in air, followed by aging at 800 °C for 6 h, cooling in air) preserved the zone structure of the weld but led to the formation of the O-phase within β-grains. The microhardness of the weld in the zone corresponds to 360±15 HV0.2, but after HT, it increased to 382±20 HV0.2. The strength properties of the welded joint after HT were above 90 % of the base metal (σ_ucs = 1120 MPa, σ_0.2 = 1090 MPa), while elongation to failure is close to the initial condition (δ = 2.1 %).

1. Goyal K., Bera C., Sardana N. Temperature-dependent structural, mechanical, and thermodynamic properties of B2-phase Ti2AlNb for aerospace applications. Journal of Materials Science. 2022;57(41):19553—19570. https://doi.org/10.1007/s10853-022-07788-3

2. Shagiev M.R., Galeyev R.M., Valiakhmetov O.R. Ti2AlNbBased intermetallic alloys and composites. Materials Physics and Mechanics. 2017;33(1):12—18. https://doi.org/10.18720/MPM.3312017_2

3. Nandy T.K., Banerjee D. Creep of the orthorhombic phase based on the intermetallic Ti2AlNb. Intermetallics. 2000;8(8):915—928. https://doi.org/10.1016/S0966-9795(00)00059-5

4. Emura S., Araoka A., Hagiwara M. B2 grain size refinement and its effect on room temperature tensile properties of a Ti—22Al—27Nb orthorhombic intermetallic alloy. Scripta Materialia. 2003;48:629—634. https://doi.org/10.1016/S1359-6462(02)00462-1

5. Kim Y.-W., Dimiduk D.M. Progress in the understanding of gamma titanium aluminides. Journal of Minerals, Metals & Materials Society. 1991;43:40—47. https://doi.org/10.1007/BF03221103

6. Kumpfert J., Leyens C. Orthorhombic titanium aluminides: Intermetallics with improved damage tolerance. In: Titanium and Titanium Alloys — Fundamentals and Applications. GmbH & Co.: Wiley—VCH Verlag, 2005. P. 59—88. https://doi.org/10.1002/3527602119.ch3

7. Li Y.-J., Wu A.-P., Li Q., Zhao Y., Zhu R.-C., Wang G.-Q. Effects of welding parameters on weld shape and residual stresses in electron beam welded Ti2AlNb alloy joints. Transactions of Nonferrous Metals Society of China. 2019;29(1):67—76. https://doi.org/10.1016/S1003-6326(18)64916-7

8. Liu X., Shao L., Ji Y., Zhao H., Wan X. Ultrasonic frequency pulse tungsten inert gas welding of Ti2AlNbbased alloy. Chinese Journal of Rare Metals. 2014;38(4): 541—547. https://doi.org/10.13373/j.cnki.cjrm.2014.04.001

9. Shao L., Wu S., Datye A., Zhao H., Petterson M., Peng W. Microstructure and mechanical properties of ultrasonic pulse frequency tungsten inert gas welded Ti— 22Al—25Nb (at.%) alloy butt joint. Journal of Materials Processing Technology. 2018;259:416—423. https://doi.org/10.1016/j.jmatprotec.2018.03.018

10. Bu Z., Ma X., Li R., Wu J., Li J. Effect of pressure on microstructure and mechanical properties of diffusion bonded joints of Ti2AlNb alloy. Journal of Aeronautical Materials. 2023;43:51—58. https://doi.org/10.11868/j.issn.1005-5053.2022.000162

11. Niu T., Jiang B., Zhang N., Wang Y. Microstructure and mechanical properties of Ti—Ti2AlNb interface. Composites and Advanced Materials. 2021;30:1—7. https://doi.org/10.1177/2633366X20929

12. Chen X., Zhang Z., Xie F., Wu X., Ma T., Li W., Sun D. Optimizing the integrity of linear friction welded Ti2AlNb alloys. Metals. 2021;11(5):802. https://doi.org/10.3390/met11050802

13. Cui D., Wu Q., Jin F., Xu C., Wang M., Wang Z., Li J., He F., Li J., Wang J. Heterogeneous deformation behaviors of an inertia friction welded Ti2AlNb joint: an in-situ study. Acta Metallurgica Sinica. 2023;36(4):611—622. https://doi.org/10.1007/s40195-022-01477-5

14. Panov D., Naumov S., Stepanov N., Sokolovsky V., Volokitina E., Kashaev N., Ventzke V., Dinse R., Riekehr S., Povolyaeva E., Nochovnaya N., Alekseev E., Zherebtsov S., Salishchev G. Effect of pre-heating and post-weld heat treatment on structure and mechanical properties of laser beam-welded Ti2AlNb-based joints. Intermetallics. 2022;143:107466. https://doi.org/10.1016/j.intermet.2022.107466

15. Naumov S.V., Panov D.O., Chernichenko R.S., Sokolovsky V.S., Volokitina E.I., Stepanov N.D., Zherebtsov S.V., Alekseev Е.B., Nochovnaya N.A., Salishchev G.A. Structure and mechanical properties of welded joints from alloy based on VTI-4 orthorhombic titanium aluminide produced by pulse laser welding. Izvestiya. Non-Ferrous Metallurgy. 2023;29(2):57—73. https://doi.org/10.17073/0021-3438-2023-2-57-73

16. Lei Z., Zhang K, Zhou H., Ni L., Chen Y. A comparative study of microstructure and tensile properties of Ti2AlNb joints prepared by laser welding and laser-additive welding with the addition of filler powder. Journal of Materials Processing Technology. 2018;255:477—487. https://doi.org/10.1016/j.jmatprotec.2017.12.044

17. Bu Z., Wu J., Ma X., Li Z., Li J. Microstructure and mechanical properties of electron beam welded joints of Ti2AlNb alloy. Journal of Materials Engineering and Performance. 2022;20:5329—5337. https://doi.org/10.1007/s11665-022-07514-9

18. Li L., Fu P., Zhao T., Tang Z., Mao Z. Effect of preheating on the microstructure evolution and mechanical properties of electron beam welded Ti2AlNb alloy. Journal of Materials Engineering and Performance. 2022;32(8): 3648—3657. https://doi.org/10.1007/s11665-022-07346-7

19. Li Y., Zhao Y., Li Q., Wu A., Zhu R., Wang G. Effects of welding condition on weld shape and distortion in electron beam welded Ti2AlNb alloy joints. Materials & Design. 2017;114:226—233. https://doi.org/10.1016/j.matdes.2016.11.083

20. Short A.B. Gas tungsten arc welding of α + β titanium alloys: A review. Materials Science and Technology. 2009;25(3):309—324. https://doi.org/10.1179/174328408X389463

21. Li Z., Cui Y., Yu Z., Liu C. In-situ fabrication of Ti2AlNb-based alloy through double-wire arc additive manufacturing. Journal of Alloys and Compounds. 2021;876: 160021. https://doi.org/10.1016/j.jallcom.2021.160021

22. Shchitsyn Yu.D., Tytkin Yu.M. Interaction of a compressed arc with a crater cavity during keyhole plasma arc welding. Svarochnoe рroizvodstvo. 1994;6:32—33. (In Russ.).

23. Stefanescu D.M., Ruxanda R. Solidification structures of titanium alloys. In: ASM Handbook Metallography and Microstructures. 2004. P. 116—126. https://doi.org/10.31399/asm.hb.v09.a0003728

24. Wu J. Xu L., Lu Z., Cui Y., Yang R. Preparation of powder metallurgy Ti—22Al—24Nb—0.5Mo alloys and electron beam welding. Acta Metallurgica Sinica. 2016;52(9): 1070—1078. https://doi.org/10.11900/0412.1961.2016.00019

25. Zhang K., Lei Z., Chen Y., Yang K., Bao Y. Heat treatment of laser-additive welded Ti2AlNb joints: Microstructure and tensile properties. Materials Science and Engineering: A. 2019;744:436—444. https://doi.org/10.1016/j.msea.2018.12.058

26. Zhang K., Ni L., Lei Z., Chen Y., Hu X. Microstructure and tensile properties of laser welded dissimilar Ti— 22Al—27Nb and TA15 joints. The International Journal of Advanced Manufacturing Technology. 2016;87:1685—1692. https://doi.org/10.1007/s00170-016-8579-3

27. Wang L., Sun D., Li H., Gu X., Shen C. Microstructures and mechanical properties of a laser-welded joint of Ti3Al—Nb alloy using pure Nb filler metal. Metals. 2018;8(10):785. https://doi.org/10.3390/met8100785

28. Chen X., Xie F.Q., Ma T.J., Li W.Y., Wu X.Q. Effects of post-weld heat treatment on microstructure and mechanical properties of linear friction welded Ti2AlNb alloy. Materials & Design. 2016;94:45—53. https://doi.org/10.1016/j.matdes.2016.01.017

29. Chen W., Chen Z.Y., Wu C.C., Li J.W., Tang Z.Y., Wang Q.J. The effect of annealing on microstructure and tensile properties of Ti—22Al—25Nb electron beam weld joint. Intermetallics. 2016;75:8—14. https://doi.org/10.1016/j.intermet.2016.02.006

30. Jiao X., Kong B., Tao W., Liu G., Ning H. Effects of annealing on microstructure and deformation uniformity of Ti—22Al—24Nb—0.5Mo laser-welded joints. Materials & Design. 2017;130:166—174. https://doi.org/10.1016/j.matdes.2017.05.005

31. Lei Z., Zhou H., Chen Y., Zhang K., Li B. A comparative study of deformation behaviors between laserwelded joints and base metal of Ti—22Al—24.5Nb— 0.5Mo alloy. Journal of Materials Engineering and Performance. 2019;28(8):5009—5020. https://doi.org/10.1007/s11665-019-04224-7

32. Lu B., Yin J., Wang Y., Yang R. Gas tungsten arc welding of Ti2AlNb based alloy sheet. In: Proc. 12th World Conf. Titan (China, Beijing, 19—24 June 2011). 2012. Vol. 1. Р. 816—818.