Chemical, microstructure, and mechanical property of TiAl alloys produced by high-power direct laser deposition

Additive manufactured metals sometimes exhibit extraordinary microstructures and mechanical properties due to the particular processes. In this paper, we focus on a novel gradient TiAl alloys fabricated by high-power direct laser deposition, whose chemical composition, microstructure, and mechanical property vary along the building direction. The results indicate that Al concentration dramatically decreases from 39.5 at.% to 30.1 at.% as the height increases from the bottom to the top. Meanwhile, microstructural characterization indicates that the specimen appears basket-weave microstructure at the bottom, then the alpha 2 and gamma phase gradually decrease, and eventually it transforms into acicular martensite microstructure in the top region. The indentation analysis shows that the associated hardness increases as the height increases, while the plasticity reaches a minimum value in the middle region. The increasing amount of beta o ( omega) is considered to be responsible for the increasing hardness because of the strong precipitation strengthening effect. The high plasticity in the bottom and top regions results from the strong deformation behaviors of the gamma and beta o phases. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This paper focuses on a novel gradient TiAl alloy fabricated by high-power direct laser deposition, which exhibits varying chemical composition, microstructure, and mechanical properties along the building direction. The results show that the aluminum concentration decreases as the height increases, leading to changes in the microstructure. The hardness increases with height while the plasticity reaches a minimum in the middle region.