Autor(es):
Barbosa, J. 
; Teodoro, O. M. N. D. ; Ribeiro, Carlos Silva ; Moutinho, A. M. C. ; Monteiro, A. Caetano
Data: 2004
Identificador Persistente: http://hdl.handle.net/1822/12445
Origem: RepositóriUM - Universidade do Minho
Assunto(s): TiAl; SIMS; Induction; Melting; Investment casting
Descrição
Titanium aluminides are arising as a valuable alternative to superalloys in applications where the
ratio resistance/density is important. Together with excellent mechanical and corrosion properties
at high temperatures, such characteristics are very attractive for applications in the aeronautical,
aerospace and automotive industries. However, the current high selling price, due to high costs of
production and raw materials and the need of very specific equipment, are limitative factors for
further applications. With the end of the cold war, and the decrease of traditional markets of TiAl,
the strategy to develop other applications, strongly depends on the decrease of production costs.
An alternative to the present production routes might be the use of traditional casting techniques,
by induction melting of the alloy in a ceramic crucible and pouring into ceramic moulds, made by
the investment casting process. However, due to the high reactivity of Ti alloys, the use of
traditional ceramic materials cannot be used, as they lead to oxide formation and oxygen pick up
both from the crucible and the moulding materials. In this work, the relative oxygen concentration
of Ti-48Al castings was measured by SIMS — Secondary Ion Mass Spectrometry. This technique
provides a direct measurement of the isotopic composition with high sensitivity. The cylindrical
samples were specially prepared to allow the analysis of the area close to the border. Oxygen
profiles were acquired for samples obtained by with different mould materials. The comparison of
such profiles with hardness profiles, give insight in the significance of the oxygen concentration in
the properties of the alloy and in the choice of the most suitable materials for TiAl production
