（1. Changzhou G-Light Additive Manufacturing Co., Ltd., Jiangsu Changzhou 213100, China；2. Central Iron
&Steel Research Institute, Beijing 100081, China； 3. Taiyuan University of Technology, Taiyuan 030002；
4. Gaona Aero Material Co., Ltd., Beijing 100081, China）
Abstract：Ti-22Al-25Nb alloy was prepared by laser selective melting process, and the influence of different
heat treatment on microstructure constitution, morphology and mechanical properties was investigated. The re‐
sults show that the as-printed microstructure has obvious anisotropy of horizontal and longitudinal, showing the
characteristics of columnar crystals growing along Z orientation. The microstructure constitution is mainly B2
phase, and there is no obvious α 2 and O phase precipitation. When the heat treatment temperature rises to
1 080 ℃, the transformation of columnar crystals to equiaxed grain will occur, and the grain boundaries have
poor ability to coordinate plastic deformation and crack propagation, resulting in lower strength and poor plastic‐
ity. Heat treatment at 960 ℃ in the O+α2+B2 three-phase region can maintain the morphology characteristics of
columnar crystals, the size of the secondary precipitated O phase is mainly related to the aging temperature, the
O-phase precipitation size decreases with the decrease of the temperature, the multi-scale O phase of disperse precipitation plays the main strengthening role, the continuous B2 phase matrix is contributed to plastic deforma‐
tion, the discontinuous precipitated phase on grain boundary is beneficial for coordinating plastic deformation
and resisting crack propagation along the crystal, the strength and elongation of HT2 and HT3 heat treatment are
higher, and the fracture also presents obvious ductile fracture characteristics. Finally, the tensile properties at
room temperature can reach the mechanical property level compared to Ti2AlNb forgings when the optimized
heat treatment is 960 ℃/2 h+820 ℃/6 h.
2023, Vol. 33 
