Synthesis and Real Structure Group

PAK 19

Al-rich Al-Ti alloys (PAK 19), Project "Electron microscopic analysis of the  microstructure and the local chemical composition".

 

Titanium aluminides rich in Aluminium are considered as promising structural materials for high temperature applications. Al-rich two-phase TiAl alloys can be compared to Ti-rich alloys to have almost stoichiometric γ-TiAl alloys at low specific weight and a  greater resistance to oxidation by preferential oxide formation expected at the surfaces. This material could therefore be of great interest for applications as high temperature material, when we are successful to produce a mechanically stable two-phase microstructure, similar to the γ-TiAl in Ti-rich alloys. Initial investigations have shown that in TiAl with Al-content between 55 at% and 65 at%, under definite manufacturing conditions, fully lamellar structure or duplex structures exist, in this case  γ-TiAl + r-TiAl. Such Al-rich TiAl alloys with regard to their microstructure have been investigated microstructurally and chemically through TEM. Through comparative samples with different heat-treated, quenched, deformed and addition of alloy additives, the existence of the coexisting phases in different areas are to be determined in order to optimize the stability of the microstructure. In Al/Ti alloys, transformations kinetics in the case of h-Al2Ti and the formation of lamellar  γ-TiAl + r-Al2Ti microstructure have been studied. (MRS – Proceedings : Kelm et.al., 2008)
In the next stages, the Al/Ti alloys with Nb and Cr additives shall be studied.