Influence of Exposure at 750℃ on Room Temperature Tensile Ductility of Cast TiAl Alloy with the Directional Lamellar Microstructure

摘要

in this study, based on cast Ti-47.5Al-2.5V-l.0Cr (at. %) alloy with the directional lamellar microstructure, the influence of exposure at 750℃ in air on room temperature tensile ductility was investigated as a function of time, ranging fromlhr to 300hr, in order to determine the onset exposure time for a significant reduction in RT ductility and the fracture mechanism for the exposed specimens. The results indicated that this alloy could still retain more than 2.0% of its ductility after exposure at 750℃ for 150hr, and its ductility decreased to 1.58% and ~1.0% even after exposure for 200hr and 300hr, respectively. High ductility for the directional lamellar microstructure could be retained after exposure for 150hr, which was attributed to its high crack origination and propagation resistance at specific lamellar orientation. And the fracture mechanism of the exposed specimen with this special structure would also be discussed.