Microstructure and tensile properties of as-cast Ti–45Al–(8–9)Nb–(W, B, Y) alloy

• Published in: Journal of alloys and compounds 2006-04, Vol.414 (1), p.131-136
• Main Authors: Xu, X.J., Lin, J.P., Wang, Y.L., Gao, J.F., Lin, Z., Chen, G.L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Casting; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Elasticity. Plasticity; Exact sciences and technology; Fractures; Intermetallics; Mechanical and acoustical properties of condensed matter; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Microstructure; Physics; Tensile properties
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2005.02.110

Microstructure and tensile properties of high Nb containing TiAl alloy, with nominal composition of Ti–45Al–(8–9)Nb–(W, B, Y) (at.%), were investigated. The results showed that the as-cast alloy had near lamellar microstructure composed of fine homogenous lamellar colonies, with a size of about 70 μm, and a small amount of β phase and equiaxed γ phase. The β phase existed either on the boundaries of the lamellar colonies in irregular morphology or in the lamellar colonies in lamellar or blocky morphology. Equiaxed γ phase existed on the boundaries of lamellar colonies. There also existed some borides in three morphologies: convoluted flakes, ribbons and particles. The alloy had mediate tensile properties at both room temperature (RT) and high temperature. At RT, ultimate tensile strength level of 668 MPa and 0.49% plastic elongation were obtained, and the brittle-to-ductile transition temperature was higher than 815 °C. Cracks propagated in transgranular mode predominantly, and borides and β phase were detrimental to the ductility of the as-cast alloy.