Microstructure and strength of diffusion-bonded joints of TiAl base alloy to steel

Journal Article · Mon Jul 15 00:00:00 EDT 2002 · Materials Characterization

DOI:https://doi.org/10.1016/S1044-5803(02)00319-4· OSTI ID:20748659

He, P; Feng, J C; Zhang, B G; Qian, Y Y

Diffusion bonding of TiAl-based alloy to steel was carried out at 850-1100 deg. C for 1-60 min under a pressure of 5-40 MPa in this paper. The relationship of the bond parameters and tensile strength of the joints was discussed, and the optimum bond parameters were obtained. When products are diffusion-bonded, the optimum bond parameters are as follows: bonding temperature is 930-960 deg. C, bonding pressure is 20-25 MPa, bonding time is 5-6 min. The maximum tensile strength of the joint is 170-185 MPa. The reaction products and the interface structures of the joints were investigated by scanning electron microscopy (SEM), electron probe X-ray microanalysis (EPMA) and X-ray diffraction (XRD). Three kinds of reaction products were observed to have formed during the diffusion bonding of TiAl-based alloy to steel, namely Ti{sub 3}Al+FeAl+FeAl{sub 2} intermetallic compounds formed close to the TiAl-based alloy. A decarbonised layer formed close to the steel and a face-centered cubic TiC formed in the middle. The interface structure of diffusion-bonded TiAl/steel joints is TiAl/Ti{sub 3}Al+FeAl+FeAl{sub 2}/TiC/decarbonised layer/steel, and this structure will not change with bond time once it forms. The formation of the intermetallic compounds results in the embrittlement of the joint and poor joint properties. The thickness of each reaction layer increases with bonding time according to a parabolic law. The activation energy Q and the growth velocity K{sub 0} of the reacting layer Ti{sub 3}Al+FeAl+FeAl{sub 2}+TiC in the diffusion-bonded joints of TiAl base alloy to steel are 203 kJ/mol and 6.07 mm{sup 2}/s, respectively. Careful control of the growth of the reacting layer Ti{sub 3}Al+FeAl+FeAl{sub 2}+TiC can influence the final joint strength.

• OSTI ID: 20748659
• Journal Information: Materials Characterization, Vol. 48, Issue 5; Other Information: PII: S1044580302003194; Copyright (c) 2002 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BONDING
DIFFUSION
ELECTRON MICROPROBE ANALYSIS
ELECTRON PROBES
EMBRITTLEMENT
FCC LATTICES
INTERFACES
INTERMETALLIC COMPOUNDS
JOINTS
LAYERS
MICROSTRUCTURE
PRESSURE RANGE MEGA PA
SCANNING ELECTRON MICROSCOPY
STEELS
TEMPERATURE RANGE 1000-4000 K
TENSILE PROPERTIES
TITANIUM CARBIDES
X-RAY DIFFRACTION