Infrared brazing of TiAl intermetallic using BAg-8 braze alloy

• Published in: Acta materialia Vol. 51; no. 7; pp. 1991 - 2004
• Main Authors: Shiue, R.K., Wu, S.K., Chen, S.Y.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 18.04.2003; Elsevier Science
• Subjects: Applied sciences; BAg-8 braze alloy; Bonding strength test; Brazing. Soldering; Exact sciences and technology; Infrared brazing; Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; Microstructure; Titanium aluminide; Bonding strength test; Microstructure; BAg-8 braze alloy; Infrared brazing; Titanium aluminide; Intermetallic compound; Shear strength; Brazing; Aluminium alloy; Braze metal; Experimental study; Titanium base alloys; Welding metallurgy; Interface; Binary alloy
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(02)00606-7

TiAl intermetallic alloy joined by infrared brazing using BAg-8 braze alloy was investigated. The microstructural evolution of the brazed joint, shear strength and reaction kinetics across the joint was comprehensively evaluated. According to the experimental observations, silver would not react with the TiAl substrate, but copper reacted vigorously with the TiAl, forming continuous reaction layer. The consumption of copper from molten braze during infrared brazing resulted in depletion of the copper content from the braze. Therefore, chemical composition of the braze deviated from Ag-Cu eutectic into hypoeutectic with increased brazing time and/or temperature. Both AlCuTi and AlCu 2Ti phase were observed at the interface between BAg-8 and TiAl substrate for the specimen brazed at 950°C. By increasing the brazing temperature and time, the growth rate of AlCuTi phase was much faster than that of AlCu 2Ti phase. The maximum shear strength achieved 343 MPa for the specimen infrared brazed at 950°C for 60 s. Further increasing the brazing time resulted in excessive growth of brittle AlCuTi reaction layer, which greatly deteriorated the shear strength of the joint.