Influence of cooling rate on microstructure formation during rapid solidification of binary TiAl alloys

• Rapid solidification studies with varying cooling rates were realized for Ti–Al.
• Experiments were combined with finite element simulations of heat transfer.
• The resulting microstructure of Ti–Al alloys is strongly dependent on the Al content.
• The microstructure and phase transformation behavior can be predicted.
• The method allows alloy development for processes involving rapid solidification.

Titanium aluminides as structural intermetallics are possible candidates for a potential weight reduction and increased performance of high temperature components. A method for the characterization of the microstructure formation in rapidly solidified alloys was developed and applied for binary Ti–(44–48)Al (at.%). The results show a strong dependency of the microstructure on the Al content at cooling rates between 6 ⋅ 102 and 1.5 ⋅ 104 K s−1. The formation of α → α2 ordering, lamellar α2 + γ colonies and interdendritic TiAl γ-phase were observed, depending on the Al amount. Based on thermodynamic calculations the observed microstructure can be explained using the CALPHAD approach taking into account the non-equilibrium conditions. The presented method provides a useful tool for alloy development for processing techniques involving rapid solidification with varying cooling rates.