J. Mater. Sci. Technol. ›› 2022, Vol. 103: 84-97.DOI: 10.1016/j.jmst.2021.06.027

• Research Article • Previous Articles     Next Articles

Seynergistic effect of Mo and Zr additions on microstructure and mechanical properties of Nb‐Ti‐Si‐based alloys additively manufactured by laser directed energy deposition

Yunlong Lia,b, Xin Lina,b,*(), Yunlong Hua,b, Jun Yua,b, Junguo Zhaoc, Hongbiao Dongc,**(), Weidong Huanga,b   

  1. aState Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
    bKey Laboratory of Metal High Performance Additive Manufacturing and Innovative Design, MIIT China, Northwestern Polytechnical University, Xi’an 710072, China
    cSchool of Engineering, University of Leicester, LE17RH, UK
  • Received:2021-01-13 Revised:2021-06-11 Accepted:2021-06-14 Published:2022-03-20 Online:2021-08-26
  • Contact: Xin Lin,Hongbiao Dong
  • About author:** hd38@leicester.ac.uk (H. Dong).
    * State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China. E-mail addresses: xlin@nwpu.edu.cn (X. Lin).

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Abstract:

The synergistic effect of Mo and Zr additions on microstructure evolution, room-temperature fracture toughness and microhardness of Nb-22Ti-15Si-xMo-yZr (x = 4,8, y = 3,6) alloys manufactured by laser directed energy deposited (L-DED) have been investigated. The major phases in as-deposited 4Mo-3Zr alloy are Nb solid solution (Nbss), Nb3Si and γ-Nb5Si3. The Nb3Si phases disappear with increasing Mo content to 8 at.% or increasing Zr content to 6%. γ-Nb5Si3 precipitates formed in the Nbss of as-deposited xMo-yZr alloys due to the cyclic re-heating, and the γ-Nb5Si3 precipitates and Nbss matrix exhibits orientation relationship (OR) of [001]Nbss//[$\bar{1}112$]γ and (110)Nbss//($01\bar{1}0$)γ in as-deposited 4Mo-6Zr alloy. The microstructure of xMo-yZr alloys became relative homogeneity and the Nbss matrix showed the better continuity after the heat treatment (1400 °C/30 h). The Nb3Si phase has transformed into Nbss and α-Nb5Si3 with the OR have been determined as {100}Nbss//{100}α and{111}Nbss//{111}α in the heat-treated 4Mo-3Zr alloy. When Mo content increase to 8at.%, a part of γ-Nb5Si3 phase also transformed into the α-Nb5Si3 phase with the OR have been determined as {$11\bar{2}0$}γ//{110}α and {$10\bar{1}0$}γ//{111}α after heat treatment. Among the as-deposited alloys, the 4Mo-6Zr alloy has the highest fracture toughness KQ with the lowest hardness. The average KQ of 4Mo-6Zr and 8Mo-6Zr alloys increased by 28% and 30% after the heat treatment, and reached 13.61 and 11.43 MPa·m1/2, respectively. The hardness of Nb-22Ti-15Si-xMo-yZr alloys is significantly decreased after the heat treatment.

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