Enhanced Hot Workability of Ti–46Al–4Nb–0.1B Alloy by Introducing Adjustable β Phase via Elemental Powder Metallurgy

Abstract

TiAl‐base alloys are a kind of promising materials for high‐temperature applications. The β phase existing in TiAl alloy can improve the hot workability, but deteriorates the creep properties. Preparing a β phase‐containing TiAl‐base alloy to enhance the hot workability before hot deformation and eliminating the β/B2 phase by postheat treatment to improve the service performance is a good strategy. Herein, a significant volume fraction of β phase is obtained in the Ti–46Al–4Nb–0.1B alloy by the elemental powder metallurgy (EPM), and the β/B2 phase is eliminated by the subsequent heat treatment. The results demonstrate that the microstructure of the EPMed Ti–46Al–4Nb–0.1B alloy predominantly consists of α2/γ lamellar colonies, equiaxial γ grains, and some randomly distributed β phase and σ‐Nb2Al phase. The β/B2 phase formed at the Nb‐enriched regions is caused by insufficient diffusion. The EPMed Ti–46Al–4Nb–0.1B alloy has a relatively low thermal deformation activation energy (Q, 410 kJ mol−1), showed a well hot workability. The existence of the β phase is advantageous to harmonize the deformation of α2/γ lamellar grains and to improve the deformability of the TiAl alloy. The subsequent heat treatment can eliminate the Nb‐enriched regions and the B2 phase to ensure good service performance.