Hydrogen absorption kinetics of porous Ti6Al4V alloys

The hydrogen absorption kinetics of porous Ti6Al4V alloys in the temperature range of 623-1023 K have been investigated. The obtained hydrogen absorption kinetic curves were fitted using a series of mechanism functions to reveal the kinetic parameters and reaction mechanisms of the hydrogen absorption process. The results show that the starting temperature of hydrogen absorption reaction in porous Ti6Al4V alloys is around 623 K, which is lower than that in dense Ti6Al4V alloys but higher than that in Ti6Al4V powders. Additionally, both the initial hydrogen absorption rate and equilibrium hydrogen pressure increase with increasing temperature. The three-dimensional diffusion process is the intrinsic rate-limiting step of hydrogen absorption between 623 K and 1023 K. The apparent activation energy calculated according to Arrhenius equation for the absorption of 1 mol H-2 into porous Ti6Al4V alloys is 14.545 kJ, which is smaller than that in dense Ti alloys. (C) 2009 Elsevier B.V. All rights reserved.