On Microstrucitural Evolution in Gas Atomized Ti-50 at.% Al-2 at.% Nb Powder

Abstract

ABSTRACTMicrostructural development in helium gas atomized Ti-50A1-2Nb (at.%) powder has been characterized using x-ray diffractometry and transmission electron microscopy. The structure of the as-atomized powder was a mixture of two phases: an ordered fct (L10)γ TiAl phase and an hcp α Ti phase containing fine (≈ 10–20 nm) D019 α2 domains. Large powder (≈ 250 μm) contained ≈ 14 volume % hcp phase, while fine powder (≈37 μm) contained ≈ 72 volume % hcp phase. However, this α+α2 constituent was metastable and transformed to the γ phase during annealing.