Elimination of inclusions and evaporation control during melting of Ti-48Al-2Cr-2Nb-1B intermetallic alloy

Titanium aluminide intermetallic compounds have an excellent capability for use in engineering structures at high temperatures. In the present work the formation of Nb rich inclusions in microstructure and evaporation of Al during melting of γ-TiAl based alloy (Ti-48Al-2Cr-2Nb-1B (at %)) was studied. The results show that the inclusions cannot be removed even with a four-stage melting process, when elemental Nb is used as raw material. However, by replacing Nb with NbAl₃ and using a three-stage melting process, the inclusions were removed from microstructure and also evaporation of Al was reduced remarkably. Otherwise, with removing elemental Al from raw material by using TiAl compound, evaporation of Al will be very low. Increasing vessel pressure from 400 to 600 mbar will not influence evaporation of Al. The article is published in the original.