Characteristics of β_2 Phase in the Casting Alloy Ti-47Al-2Cr-2Nb and its Effect on the Alloy Thermal Stability

The characteristics of β2 phase and its effects on the alloy thermal stability were investigated in the casting alloy Ti-47Al-2Cr-2Nb with industrial application value.The results show that β2 phase is with high Cr content and of dispersive distribution and continuous linear morphology in the TiAl alloy lamellar microstructure.No strict coherent orientation of α2 and γ phase is kept in β2 phase.By aging treatment(1 150 ℃ and 48 h),the lamellar structure is dissolved and coarsened preferentially at the phase interface between β2 and(α2+γ).During the heating process of(α2+γ) phase region,α2 particles are also precipitated and grown preferentially at the boundary.Accordingly,the addition of β2 phase is harmful for the thermal stability of TiAl alloy.