A study on the chemical and microstructural optimization of the Ti-48-2-2 alloy processed by Electron Beam Melting

Engineering titanium aluminide (TiAl) alloys are a family of intermetallic materials that, thanks to their outstanding specific mechanical properties, attracted significant attention for high-temperature automotive and aerospace applications. One of the key-points for the introduction of TiAl alloys as jet turbines for the next generation of aircraft engines is related to the sustainable weight reduction. Electron Beam Melting (EBM) already proved to be a promising process for TiAl alloys production, however further efforts are necessary in the comprehension of the role of the process parameters in order to better understand their relationship with residual porosity, Al loss and homogeneity of the microstructure. In order to improve the final properties, in this work a study of the EBM process as well as the subsequent heat treatment has been carried out on Ti-48Al-2Cr-2Nb (at. %) alloy and two slight modified chemical compositions. Theoretical-experimental analysis has been combined with the use of simulation tools to speed up the optimisation of both chemical composition and process parameters for EBM production. Such a combined approach was conducted regarding the influence of Al loss during the EBM process on phase fraction and phase transition temperatures. Additionally, heat treatment studies were carried out to further optimize the microstructure.