Effect of scanning speed on microstructure and mechanical properties of as-printed Ti–22Al–25Nb intermetallic by laser powder bed fusion

Abstract

Ti–22Al–25Nb alloy is a lightweight, high-performance, and high-temperature material with broad application prospects in aerospace. Laser powder bed fusion (LPBF) enables the rapid manufacture of Ti–22Al–25Nb (at. %) powder into complex, high-precision parts for various applications. This paper provides an in-depth analysis of how scanning speed affects the microstructure and mechanical properties of Ti–22Al–25Nb alloy prepared by LPBF. The goal of this study is to improve the mechanical properties and the printing efficiency in the future. The temperature distribution in the printing process was studied by finite element simulation, and the effect of scanning speed was analyzed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that increasing the scanning speed improved the cooling rate of the liquid melt, which decreases the grain size of the β phase and increases of the dislocation density. At the same time, a significant amount of the O phase precipitates along the grain boundaries. Excellent elongation (15%) and yield strength (982 MPa) are obtained due to the pinning of the nano-O phase, a fine grain, and good relative density when the scanning speed is 0.6 and 0.8 m/s, respectively.