|Preparation of TiAl-based alloys by induction melting in graphite crucibles|
CEGAN, T., SZURMAN, I., KURSA, M., HOLEŠINSKÝ, J., VONTOROVÁ, J.
vol. 53 (2015), no. 2, pp. 69 - 78
Three TiAl-based alloys with nominal composition Ti-47Al-8Nb, Ti-47Al-8Ta and Ti-47Al-8Ta-0.3Y (at.%) were prepared by induction melting in graphite crucibles and centrifugal casting into graphite moulds. Chemical composition, microstructure and mechanical properties of the as-cast alloys are characterised. The melting in the graphite crucible leads to an increase of carbon content from 460 to 1020 wtppm and formation of fine carbide particles predominantly in the γ(TiAl) phase. Beside fine carbides, the addition of 0.3 at.% of yttrium results in formation of fine Y2O3 and YAl2 particles. The oxygen content depends on the chemical composition and varies between 330 and 780 wtppm for Ta and Nb containing alloys, respectively. The as-cast alloys exhibit relatively high values of room-temperature compression yield strength up to 922 MPa, ultimate compression strength up to 1793 MPa and plastic deformation to fracture up to 24.3 %. The compression yield strength increases linearly with increasing Vickers microhardness of the as-cast alloys. From the point of view of chemical composition, microstructure and studied mechanical properties, induction melting in the graphite crucible and centrifugal casting into graphite mould can be considered as a suitable method of preparation of TiAl-based alloys.
titanium aluminides, TiAl, induction melting, graphite crucible, microstructure, mechanical properties
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