Features of feathery γ structure in a near-γ TiAl alloy

This work characterizes the feathery-like structures produced in a Ti-46.8Al-1.7Cr-1.8Nb (at.%) alloy during rapid continuous cooling from the α domain. Their morphology and crystallography are described using different microscopy and orientation mapping techniques. These feathery-like structures are divided into many small domains, characterized by low-angle misorientations (rotated less than 15°) between the domains. The domains comprise multiple parallel γ lamellae and rare traces of α2. These lamellae follow the Blackburn orientation relationship and have a {1 1 1}γ habit plane. Two types of γ-feathery structures were identified according to their location and crystallography. The grain-boundary γ-feathery structures originate from lamellar structures that grow into a neighboring grain. Alternatively, the internal γ-feathery structures are located in the interior of prior α grains and show an average misorientation of 36° around one 〈100〉γL axis of the lamellar structure in which it is embedded. This paper describes these two γ-feathery structures in detail and discusses their development in light of the mechanisms available in the literature, particularly sympathetic nucleation.