Intragranular nucleation sites of massive γ grains in a TiAl-based alloy

Massive γ grains were generated in a TiAl-based alloy through ice-water quenching from the α domain. Apart from those located along α2/α2 grain boundaries, a few massive γ grains were detected inside the α2 grains. Some of these intragranular grains were revealed to be attached to particular α2 twins (K1: “{2¯1210¯3}” η1: 〈51¯4¯6¯〉), in a Blackburn orientation relationship with them. Others were identified as developing in feathery colonies of similar crystallographic orientation. Whatever the nucleation site, further growth of all massive γ grains involves successive twinning on {1 1 1}γ planes.