The directional solidification, microstructural characterization and deformation behavior of β-solidifying TiAl alloy

Abstract

A β-solidifying Ti-43Al-2Cr-2Mn-0.2Y alloy was directionally solidified by the optical floating zone melting method. The microstructure is mainly characterized by /α2 lamellae with specific orientations, which exhibits straight boundaries. The β phase is randomly distributed in the lamellarmicrostructure, indicating that the β phase cannot be directionally solidified. The directional solidification of /α2 lamellae was not affected by the precipitation of the β phase. Hot compression tests show that the deformation behavior of the β-containing lamellar microstructure also exhibits the anisotropic characteristic. The deformation resistance of the lamellae is lowest when the loading axis is aligned 45° to the lamellar interface. Microstructural observation shows that the decomposition of the lamellar microstructure tends to begin around the β phase, which benefits from the promotion of a soft β phase in the deformation. Moreover, the deformationmechanismof the lamellarmicrostructure was also studied. The bulging of the γ phase boundaries, the decomposition of α2 lamellae and the disappearance of γ/γ interfaces were considered as the main coarsening mechanisms of the lamellar microstructure.