Effect of β-phase stabilizing elements and high temperature (1373-1693 K) on hydrogen absorption in TiAl alloys

In this research work, the effect of β-phase stabilizing elements (Nb, Cr, V) and high temperature (1373-1693 K) on hydrogen absorption in TiAl alloys was investigated. The results show that hydrogen content increases with increasing of hydrogenation temperature, hydrogenation time, hydrogen flow rate and the volume fraction of α2 phase and B2 phase, the maximum hydrogen content in Ti44Al6Nb1Cr2V alloy is 0.126 wt.%. Hydrogen absorption in TiAl alloys is an endothermic reaction and the heat of solution of hydrogen in Ti44Al, Ti48Al and Ti44Al6Nb1Cr2V alloys is calculated as 86.0 kJ/mol, 76.2 kJ/mol and 82.9 kJ/mol respectively, which increases with increasing of Ti content and β-phase stabilizing elements. Hydrogen promotes the size of lamellar colonies and lamellar spacing, the lamellar colony boundary of hydrogenated alloy is smooth compared with that of unhydrogenated alloy. The nanohardness of Ti44Al alloy is decreased from 3.9 GPa to 3.5 GPa after hydrogenation and the elasticity modulus is decreased from 189.2 GPa to 178.6 GPa. As hydrogen content increases, the compressive strength of TiAl alloys is decreased while the fracture strain is slightly increased indicating that hydrogen promotes a softening effect in TiAl alloys.