Effects of Nb content on microstructure and mechanical properties of Ti-Al-Nb alloys fabricated by laser-directed energy deposition
YUAN Xiaohui1,2, LI Ruidi1,2, YUAN Tiechui1,2
1. Powder Metallurgy Research Institute, Central South University, Changsha 410083, China; 2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
Abstract：The microstructure of the Ti-Al alloys fabricated by laser-directed energy deposition (LDED) often exhibits coarse columnar grains through several melten pools, which makes it difficult to obtain uniform mechanical properties. In this paper, Nb was selected as an additive element of Ti-Al binary alloys, and a series of Ti-6Al-xNb (x=5, 6.5, 7.5; mass fraction) ternary alloys were fabricated by LDED. The microstructure, room temperature tensile properties, and deformation mechanism of the alloys were characterized by optical microscope, X-ray diffractometer, scanning electron microscope, and electron backscattering diffractometer. The effects of Nb content on the microstructure and tensile properties of LDED Ti alloys were investigated. The results show that the microstructures of the alloys with different Nb contents are similar, which are mainly composed of elongated acicular or lamellar α/α′ phase, and there are a small amount of residual β phase. The alloy has the highest ultimate tensile strength ((902±35) MPa) and yield strength ((849±20) MPa) when the mass fraction of Nb is 6.5%, which is mainly attributed to the reduction in grain size. In addition, the elongation of these alloys decrease gradually with increasing Nb content. The lowest elongation of (10.2±1.4)% can be observed when the mass fraction of Nb is 7.5%.
袁晓慧, 李瑞迪, 袁铁锤. Nb含量对激光定向能量沉积Ti-Al-Nb合金组织与力学性能的影响[J]. 粉末冶金材料科学与工程, 2025, 30(3): 204-214.
YUAN Xiaohui, LI Ruidi, YUAN Tiechui. Effects of Nb content on microstructure and mechanical properties of Ti-Al-Nb alloys fabricated by laser-directed energy deposition. Materials Science and Engineering of Powder Metallurgy, 2025, 30(3): 204-214.
[1] LAI M J, LI T, RAABE D.ω phase acts as a switch between dislocation channeling and joint twinning-and transformation- induced plasticity in a metastable β titanium alloy[J]. Acta Materialia, 2018, 151: 67-77. [2] ANIL KUMAR V, GUPTA R K, PRASAD M J N V, et al. Recent advances in processing of titanium alloys and titanium aluminides for space applications: a review[J]. Journal of Materials Research, 2021, 36(3): 689-716. [3] SHEN J, ZHANG Z H, XIE J X.Simultaneously enhancing the hot workability and room-temperature strength of Ti-6Al-4V alloy via adding Mo and Fe[J]. Journal of Materials Science & Technology, 2024, 180: 32-44. [4] SVETLIZKY D, DAS M, ZHENG B L, et al.Directed energy deposition (DED) additive manufacturing: physical characteristics, defects, challenges and applications[J]. Materials Today, 2021, 49: 271-295. [5] BHARDWAJ T, SHUKLA M, PAUL C P, et al.Direct energy deposition-laser additive manufacturing of titanium- molybdenum alloy: parametric studies, microstructure and mechanical properties[J]. Journal of Alloys and Compounds, 2019, 787: 1238-1248. [6] AWANNEGBE E, LI H J, SONG T T, et al.Microstructural characterisation and mechanical evaluation of Ti-15Mo manufactured by laser metal deposition[J]. Journal of Alloys and Compounds, 2023, 947: 169553. [7] WANG Y T, LI J, XIA X Z, et al.A novel Al-Cr-Sc-Zr alloy additively manufactured via laser directed energy deposition: microstructure, phase analysis and mechanical properties[J]. Journal of Materials Processing Technology, 2023, 322: 118204. [8] XU R, LI R D, YUAN T C, et al.Towards the hydrogen pore in additively manufactured AlMgScZr alloy: influencing factors, formation kinetics mechanism[J]. Journal of Materials Science & Technology, 2024, 199: 125-144. [9] TONG Z P, WAN W B, LIU H L, et al.Combination of annealing and laser shock peening for tailoring microstructure and mechanical properties of laser directed energy deposited CrMnFeCoNi high-entropy alloy[J]. Additive Manufacturing, 2023, 61: 103345. [10] ZHANG T M, CHEN C, LI R D, et al.Effect of Cr content on the microstructure and mechanical properties of Ti-Cr alloys manufactured by laser directed energy deposition[J]. Materials Science and Engineering A, 2024, 893: 146143. [11] TAN C L, LI R S, SU J L, et al.Review on field assisted metal additive manufacturing[J]. International Journal of Machine Tools and Manufacture, 2023, 189: 104032. [12] 何坤, 郝巨, 陈素明, 等. 基于激光选区熔化工艺制备的TC4制件应用研究[J]. 铸造技术, 2022, 43(10): 924-928. HE Kun, HAO Ju, CHEN Suming, et al.Application performance research of TC4 by selective laser melting[J]. Foundry Technology, 2022, 43(10): 924-928. [13] WANG T, ZHU Y Y, ZHANG S Q, et al.Grain morphology evolution behavior of titanium alloy components during laser melting deposition additive manufacturing[J]. Journal of Alloys and Compounds, 2015, 632: 505-513. [14] CHANG K, WANG X, LIANG E Q, et al.On the texture and mechanical property anisotropy of Ti6Al4V alloy fabricated by powder-bed based laser additive manufacturing[J]. Vacuum, 2020, 181: 109732. [15] 袁晓慧, 李瑞迪, 柯林达, 等. 激光定向能量沉积Ti-6Al合金的组织与性能研究[J]. 铸造技术, 2024, 45(9): 838-846. YUAN Xiaohui, LI Ruidi, KE Linda, et al.Microstructure and mechanical properties of Ti-6Al alloy fabricated via laser-directed energy deposition[J]. Foundry Technology, 2024, 45(9): 838-846. [16] ZHANG D Y, QIU D, GIBSON M A, et al.Additive manufacturing of ultrafine-grained high-strength titanium alloys[J]. Nature, 2019, 576(7785): 91-95. [17] LU Y, TANG H B, FANG Y L, et al.Microstructure evolution of sub-critical annealed laser deposited Ti-6Al-4V alloy[J]. Materials & Design, 2012, 37: 56-63. [18] ZHU Y Y, LIU D, TIAN X J, et al.Characterization of microstructure and mechanical properties of laser melting deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy[J]. Materials & Design, 2014, 56: 445-453. [19] YANG H W, HAN Y.Enhanced corrosion fatigue strength of additively manufactured graded porous scaffold-coated Ti-6Al-7Nb alloy[J]. Journal of Materials Science & Technology, 2025, 212: 192-206. [20] BOLZONI L, RUIZ-NAVAS E M, GORDO E. Evaluation of the mechanical properties of powder metallurgy Ti-6Al-7Nb alloy[J]. Journal of the Mechanical Behavior of Biomedical Materials, 2017, 67: 110-116. [21] MANOGAR B, YANG F, BOLZONI L.Effect of Nb addition on the phase stability, microstructure, and mechanical properties of powder metallurgy Ti-5Fe-xNb alloys[J]. Metals, 2022, 12(9): 1528. [22] GÖLBAŞı Z, ÖZTÜRK B, SÜNBÜL S E, et al. Mechanical, wear and corrosion behavior of Ti-6Al-xNb (x=3.5-21wt%) alloys manufactured by powder metallurgy[J]. Powder Technology, 2023, 426: 118696. [23] CHOI G, CHOI W S, HAN J, et al.Additive manufacturing of titanium-base alloys with equiaxed microstructures using powder blends[J]. Additive Manufacturing, 2020, 36: 101467. [24] BERMINGHAM M J, MCDONALD S D, STJOHN D H, et al.Beryllium as a grain refiner in titanium alloys[J]. Journal of Alloys and Compounds, 2009, 481(1/2): L20-L23. [25] LIN C, LIU Z L, ZHAO Y Q.Theoretical research on phase transformations in metastable β-titanium alloys[J]. Metallurgical and Materials Transactions A, 2009, 40: 1049-1058. [26] 李敬. 选区激光熔化成型Ti6Al4V及其多孔结构的工艺与性能研究[D] . 广州: 华南理工大学, 2018. LI Jing.Study on the processing parameters and properties of Ti6Al4V and its porous structures fabricated by selective laser melting[D]. Guangzhou: South China University of Technology, 2018. [27] CALCAGNOTTO M, PONGE D, DEMIR E, et al.Orientation gradients and geometrically necessary dislocations in ultrafine grained dual-phase steels studied by 2D and 3D EBSD[J]. Materials Science and Engineering A, 2010, 527(10/11): 2738-2746. [28] ZHANG X, XU H, LI Z J, et al.Effect of the scanning strategy on microstructure and mechanical anisotropy of Hastelloy X superalloy produced by laser powder bed fusion[J]. Materials Characterization, 2021, 173: 110951. [29] FENG Y X, SHANG J X, LIU Z H, et al.The energy and structure of (110) twist grain boundary in tungsten[J]. Applied Surface Science, 2015, 357: 262-267.
2025, Vol. 30 
