Microstructure of SiC / TiAl Interface Formed by Solid-State Diffusion Bonding

The microstructure of the solid-state diffusion bonded interfaces of silicon carbide (SiC) and titanium aluminide (TiAl) were investigated. A 100-µm-thick Ti-48at%Al foil was inserted between two SiC specimens and then heat-treated in vacuum. The interfacial microstructure has been analyzed by scanning electron microscopy, electron probe microanalysis and X-ray diffractometry. Four layers of reaction products are formed at the interface by diffusion bonding: a layer of TiC adjacent to SiC followed by a diphase layer of TiC+Ti2AlC, a layer of Ti5Si3CX containing Ti2AlC particles and a layer of TiAl2. However, the TiAl2 layer is formed during cooling. The actual phase sequence at the bonding temperatures of 1573 K and 1673 K are described as SiC/TiC/(TiC+ Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti1-XAl1+X/TiAl and SiC/TiC/(TiC+Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti5Al11 /Ti1-XAl1+X/TiAl, respectively. The phase sequences are successfully expressed on the basis of the Ti-Al-Si-C quaternary chemical potential diagram.

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Interfacial Microstructure of Silicon Carbide and Titanium Aluminide Joints Produced by Solid-State Diffusion Bonding

MATERIALS TRANSACTIONS ◽

10.2320/matertrans.45.2734 ◽

2004 ◽

Vol 45 (8) ◽

pp. 2734-2739 ◽

Cited By ~ 7

Author(s):

Kazuyuki Tenyama ◽

Masakatsu Maeda ◽

Toshiya Shibayanagi ◽

Masaaki Naka

Keyword(s):

Silicon Carbide ◽

Solid State ◽

Diffusion Bonding ◽

Titanium Aluminide ◽

Interfacial Microstructure ◽

Solid State Diffusion ◽

State Diffusion

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Bonding γ-TiAl Alloys Using Ti/Al Nanolayers Doped with Ag

Materials Science Forum ◽

10.4028/www.scientific.net/msf.587-588.488 ◽

2008 ◽

Vol 587-588 ◽

pp. 488-491 ◽

Cited By ~ 3

Author(s):

Liliana I. Duarte ◽

Filomena Viana ◽

Manuel F. Vieira ◽

Ana Sofia Ramos ◽

M. Teresa Vieira ◽

...

Keyword(s):

Solid State ◽

Diffusion Bonding ◽

Titanium Aluminide ◽

Titanium Aluminides ◽

Bonding Temperature ◽

Bonding Interface ◽

Chemical Compositions ◽

Solid State Diffusion ◽

Fine Grained ◽

State Diffusion

Successful solid state bonding of titanium aluminides requires the use of high temperature and pressure. In previous works, authors have demonstrated that the use of Ti/Al multilayer thin film as an interlayer, deposited by d.c. magnetron sputtering onto the joining surfaces, can effectively lower the bonding temperature. The enhanced diffusivity of these nanometric layers and the heat evolved by the formation of γ-TiAl improves the joinability of titanium aluminide by solid-state diffusion bonding. In the present work, further improvement of the process was pursued by doping the interlayer with 2.8 at.% of Ag; previous studies have confirmed that silver favours the transformation Ti+Al→γ-TiAl. The solid-state diffusion bonding experiments were performed in vacuum by applying 50 MPa at 900°C for 1 h. The effect of the third element on the microstructure and chemical composition along the bonding interface has been analyzed. Microstructural characterisation of the interface was performed by scanning and transmission electron microscopy. Chemical compositions were analysed by energy dispersive X-ray spectroscopy. No defects were observed at the interface and sound bonding was achieved between the interlayers and base γ-TiAl. The bonding interface shows a fine-grained microstructure, slightly coarser than the one formed at the same temperature with the undoped Ti/Al multilayer.

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