• CN: 11-2187/TH
  • ISSN: 0577-6686

Journal of Mechanical Engineering ›› 2024, Vol. 60 ›› Issue (8): 176-185.doi: 10.3901/JME.2024.08.176

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Effect of Brazing Time on TiAl Joint Brazed with TiH2-65Ni+TiB2 Filler

LI Li1,2,3, WANG Yixuan1,2, LUO Fen1,2, ZHANG Wentao1,2, ZHAO Wei1,2, LI Xiaoqiang3   

  1. 1. School of Materials Science and Engineering, East China Jiaotong University, Nanchang 330013;
    2. State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure, East China Jiaotong University, Nanchang 330013;
    3. National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510641
  • Received:2023-05-16 Revised:2023-11-15 Online:2024-04-20 Published:2024-06-17

Abstract: Based on the activation energy calculated using Kissinger equation, an optimal powder filler containing 8.16 wt.% TiB2 is obtained from the mechanical milling (TiH2-65Ni)1-x(TiB2)x(x=0-17.70wt.%) powder fillers and used to braze Ti-47Al-2Nb-2Cr-0.15B (at.%) alloy at 1 230 ℃. The interfacial microstructure and formation mechanism of the TiAl brazed joint as well as effect of brazing time varied 0 from 20 min on their interfacial microstructures and shear strengths are systematically investigated. Furthermore, the strengthening mechanism of TiB whiskers is revealed based on detailed analysis of the relationship between interfacial microstructure and shear strength of the TiAl brazed joints. Results show that the interfacial microstructures of the TiAl brazed joints are γ-TiAl/α2-Ti3Al+τ3-Al3NiTi2 (layer Ⅰ)/τ3-Al3NiTi22-Ti3Al (layer Ⅱ)/α2-Ti3Al+τ3-Al3NiTi2+TiB (layer Ⅲ)/τ3-Al3NiTi22-Ti3Al (layer Ⅱ)/α2-Ti3Al+τ3-Al3NiTi2(layer Ⅰ)/γ-TiAl. With increasing of brazing time, the aspect ratio of TiB whiskers possessing good thermodynamic compatibility with the brazing seam matrix first increase and then agglomerate, the existed microvoids in brazing seam first disappear and then appear again, microcracks and high residual stress occur in brazing seam at overlong brazing time, resulting in increasing first and then a sharp reduction for the shear strength of the TiAl brazed joint. The maximum shear strength of 332.87 MPa for the TiAl brazed joint is obtained when the brazing time is 10 min and it brittlely fractures in layer II in quasi-cleavage mode. More TiB whiskers with large aspect ratio are expected to generate via regulating the dissolution and diffusion of TiAl alloy caused by changing brazing time in order to refine the microstructure and homogenize the phase distribution of the brazed joint, which can provide technical support for the popularization together with application and excellent brazing of TiAl alloy.

Key words: Ti-based powder filler, TiAl alloy, brazing time, interfacial microstructure, shear strength

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