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Effects of Brazing Filler Composition and Brazing Temperature on the Microstructure and Mechanical Properties of Ti2AlNb and GH4169 Alloy Brazed Joints
ZHANG Zhenyang, WANG Jingkuan, LI Peng, WANG Yinchen, LI Chao, ZHANG Liangliang, DONG Honggang
Journal of Mechanical Engineering
2024, 60 (22):
116-129.
DOI: 10.3901/JME.2024.22.116
Sound joining of Ti2AlNb alloy to GH4169 alloy is crucial for reducing the weight of aircraft, enhancing flight efficiency, and expanding the application range of Ti2AlNb alloy. Addressing the issue of significant residual stresses and the formation of various brittle TiNi intermetallic compounds in joints between titanium-aluminum alloys and nickel-based superalloys after welding, this study designed a high-entropy amorphous brazing filler with an approximate 1∶1 ratio of Ti-group elements to Ni-group elements, specifically (TiZrHf)50(NiCu)45Al5, based on the principle of interfacial compatibility. The research focused on the effects of different brazing filler compositions and brazing temperatures on the interfacial microstructure and properties of brazed joints between Ti2AlNb and GH4169 alloys. The results indicated that the typical interfacial structure of brazed joints using (TiZrHf)50(NiCu)45Al5 consisted of Ti2AlNb alloy/B2 phase dissolved with Ni and Cu (Zone I)/(Ti, Zr, Hf)(Ni, Cu, Al)2 + (Ti, Zr, Hf)(Ni, Cu)2 (Zone II)/(Ni, Cr, Fe, Ti)ss + (Ni, Cr, Fe)ss (Zone III)/GH4169 alloy. The composition of the brazing filler and the brazing temperature significantly influenced the formation and evolution of reactive phases in Zone II of the brazed seam. Using (TiZrHf)30(NiCu)65Al5, Zone II primarily consisted of (Ti, Zr)(Ni, Cu, Al)2, Al(Ni, Cu)2Ti, and Ti(Ni, Cu)2 phases, while using (TiZrHf)40(NiCu)55Al5, Zone II predominantly featured (Ti, Zr, Hf)(Ni, Cu) phases. As the brazing temperature increased, the thickness of Zone II first decreased and then increased. Brazed joints using (TiZrHf)50(NiCu)45Al5 reached a maximum shear strength of 305 MPa at 1 035 ℃ for 15 min. Fracture primarily occurred at the interface between the base material and the brazing filler, and with increasing brazing temperature, the fracture location gradually shifted to Zone II, displaying typical cleavage fracture characteristics. The formation mechanism of the joint interface structure could be categorized into four stages: solid-state diffusion of atoms, formation of liquid phase and metallurgical reactions, isothermal diffusion solidification, and growth and evolution of reactive phases.
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