The formation and Kr-ion irradiation behaviour of new microstructural features in additively manufactured titanium aluminium alloy

Abstract New microstructural features were found in the TiAl alloy manufactured using the gas tungsten arc welding-based additive manufacturing technology. The ion-irradiation responses of the new microstructure features were investigated in-situ via irradiation with 1 MeV Kr2+ ions at room and 873 K. Examination of the microstructure showed that the typical lamellar microstructure consisting of α2-Ti3Al and γ-TiAl phases formed α2/γ lamellar interfaces and γ/γ twin boundaries. Apart from this, the γ lamellae were also found to form γ/γ lamellar boundaries with the two γ lamellae in the same orientation or the // orientation relationship. This is not observed in the TiAl alloys fabricated using traditional alloy fabrication methods. Kr ion-irradiation at room and elevated temperatures resulted in no significant difference in the morphologies of most radiation-induced defects in the orientated γ lamellae and the orientated γ lamellae. However, the areas of the new boundaries exhibited different damage morphologies in comparison with the traditional γ/γ twin boundaries. The formation mechanisms of the new microstructural features formed in the additive manufacturing process and their irradiation behaviour are investigated and discussed.