Mechanisms of Improvement of High Temperature Deformability of Ti-43Al-9V-0.3Y Alloy with Addition of Y

The effects of yttrium additions on plastic deformability and the change of microstructures after deformation of TiAl alloys were investigated by hot-compression pressing. The compositions studied are Ti-43Al-9V (%) and Ti-43Al-9V-0.3Y (%). Before the hot-compression, all the samples were homogenized at 900 ℃ for 48 h and treated by hot isostatic pressing at 1250 ℃ for 4 h under an argon pressure of 170 MPa. The hot-compression experiments were conducted with the Gleeble-1500D style of thermo-force analogue machine at the temperatures of 1100, 1150, 1200 ℃ and strain rates of 1.0, 0.1, 0.01 s^(-1). The results show that the addition of yttrium can remarkably improve hot-compression deformability of Ti-43Al-9V alloy. Analysisically, main reasons for the improvement are that Ti-43Al-9V-0.3Y alloy possesses some characteristics, such as smaller grain size, lower resistance of deformation and deformation activation energy, and faster recrystallization and smaller homogeneous recrystallized grains.