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

Abstract

Massive γ grains were generated in a TiAl-based alloy through ice-water quenching from the α domain. Apart from those located along α 2 /α 2 grain boundaries, a few massive γ grains were detected inside the α 2 grains. Some of these intragranular grains were revealed to be attached to particular α 2 twins ( K 1 : “ { 2 ¯ 12 10 ¯ 3 } ” η 1 : 〈 5 1 ¯ 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.