The ambient temperature tensile behavior of duplex γ-TiAl-based alloys

Microstructural control of duplex TiAl alloys was carried out by different heat-treatment processes for the composition Ti–46.5Al–2.0Cr–1.5Nb–1.0V (at.%). The microstructures obtained had grain sizes ranging from 16 to 51 μm and volume fractions of lamellar grains ranging from 6 to 95%, respectively. Conventional ambient temperature tensile tests were performed at different strain rates in air. The results revealed strong influences of microstructure and strain rate on the mechanical properties of the alloy at ambient temperature. The yield strength of duplex TiAl alloys increases with the increase of lamellar grain fraction, but the ductility changes in a contrary way. TiAl alloys with near-gamma (NG) microstructure have the best ductility. The relationship between the yield strength and the grain size obeyed the Hall–Patch relation. The effect of strain rate on the mechanical behavior is relatively complex at ambient temperature; it changes along with the variety of microstructures. Finally, micro-deformation mechanisms causing these phenomena were investigated.