Deformation and Phase Transformation of Disordered α Phase in the (α + γ) Two-Phase Region of a High-Nb TiAl Alloy

Abstract

In this paper, the deformation and phase transformation of disordered α phase in the (α + γ) two-phase region in as-forged Ti-44Al-8Nb-(W, B, Y) alloy were investigated by hot-compression and hot-packed rolling. The detailed microstructural evolution demonstrated that the deformed microstructure was significantly affected by the deformation conditions, and the microstructure differences were mainly due to the use of a lower temperature and strain rate. Finer α grains were formed by the continuous dynamic recrystallization of α lamellae and α grains distributed around lamellar colonies. Moreover, the grooved γ grains formed by the phase transformation from α lamellae during hot rolling cooperated with and decomposed α lamellae. A microstructure evolution model was built for the TiAl alloy at 1250 °C during hot rolling.

Microstructure Sensitivity on Environmental Embrittlement of a High Nb Containing TiAl Alloy under Different Atmospheres

“…The brittleness of a TiAl alloy can be divided into intrinsic brittleness and environmental embrittlement. In view of the intrinsic brittleness problem, researchers have done a lot of effective work in composition design, microstructure control and the structure–activity relationship, which have significantly improved mechanical properties of TiAl alloys [ 10 , 11 ]. In the research of alloying, the addition of niobium (chemical symbol Nb, atomic number 41) is widely covered.…”