Effect of Nb additions on microstructure and properties of γ-TiAl based alloys fabricated by selective laser melting
(Key Laboratory of Materials Modification by Laser, Ion and Electron Beam, Dalian University of Technology, Dalian 116024, China)
Abstract: The γ-TiAl based Ti-Al-Mn-Nb alloys with different Nb additions were fabricated by selective laser melting (SLM) on the TC4 substrate. The effects of Nb content on microstructure and properties of the alloys were investigated. The results reveal that the alloys consist of γ-TiAl phase with tetragonal lattice structure and α2-Ti3Al phase with hcp lattice structure, and show a sequential structure change from near full dendrite to near lamellar structure with the increase of Nb addition. Owing to the higher Nb content in γ-TiAl phase and the formation of near lamellar structure, the alloy with 7.0 at.% Nb addition has the best combination of properties among the studied alloys, namely, not only a high hardness of HV 2000, a high strength of 1390 MPa and a plastic deformation of about 24.5%, but also good tribological properties and high-temperature oxidation resistance.
Key words: selective laser melting; γ-TiAl based alloys; microstructure; properties; Nb additions