Abstract:The tensile properties and fracture behaviors of Ti-22Al-27Nb and Ti-22Al-20Nb-7Ta alloys were investigated in the temperature range of 25～800℃. Three typical microstructures were obtained by different thermomechanical processing techniques. The results indicate that the duplex microstructure has an optimum combination of tensile yield strength and ductility both at room and elevated temperatures. Adding Ta to Ti₂AlNb alloy can improve the yield strength, especially at high temperature while retain a good ductility. The study on crack initiation and propagation in deformed microstructure of Ti₂AlNb alloys indicates that microstructure has important effect on the tensile fracture mechanism of the alloys. The cracks initiate within primary O/α₂ grains along O/B2 boundaries or O phase laths in B2 matrix, and propagate along primary B2 grain boundaries for the duplex microstructure. The fracture mode is transgranular with ductile dimples for the duplex and the equiaxed microstructures, but intergranular for the lath microstructure.

Key words: Ti₂AlNb based alloy; microstructure; property; fracture