Combustion-synthesised TiAl/NiAl layered intermetallic composite: synthesis, phase composition, and microstructure

ABSTRACT

The joining of different intermetallics (e.g. NiAl, TiAl) is important for high-temperature applications. In this study, self-propagating high-temperature synthesis was used for simultaneous joining of (Ni+Al) and (Ti+Al) layered samples of the stoichiometric compositions. The main advantage of such joining by self-propagating high-temperature synthesis is that it could be done at ambient temperature without the use of a furnace. The applied load during combustion synthesis was used to improve the contact between the Ni-Al and Ti-Al layers. The obtained results demonstrate that TiAl/NiAl intermetallics were successfully joined together with a bonding interface of about 170 μm thickness. XRD analysis has shown that the joining area consists of NiAl, TiAl, Ti₃Al, and NiTiAl₂ phases. The SEM data analysis of the transition zone of NiAl-TiAl conjunction has revealed that the transition zone consists of several intermediate layers: a polycrystalline NiAl layer; an intermediate layer based on Ni-Al-Ti containing NiTiAl₂ phase; a layer based on Ni-Al-Ti with mixed dendritic and eutectic regions; and a polycrystalline TiAl layer.The measured microhardness of the transition zone varies from 3200 up to 13,600 MPa with the maximum microhardness of 1355 ± 45 MPa corresponding to the layer identified as the NiTiAl₂ phase.

KEYWORDS:

• Intermetallic joints
• joining
• TiAl
• NiAl
• microstructure
• transition zone
• microhardness

Acknowledgements

The authors thank A.F. Belikova for microhardness measurements.

The work was carried out within Russian state assignment for the Merzhanov Institute of Structural Macrokinetics and Materials Science (ISMAN).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conceptualisation, A.E.S.; methodology, A.E.S.; investigation, M.L.B., O.D.B. and A.F.B.; writing – original draft preparation, M.L.B. and A.E.S.; writing – review and editing, M.L.B. and A.E.S. All authors have read and agreed to the published version of the manuscript.

Additional information

Funding

This work was supported by the The work is supported by the state task of A.G. Merzhanov Institute of Structural Macrokinetics and Materials Science of the Russian Academy of Sciences (ISMAN)).