Hydrogen absorption and desorption by Ti, Ti-5Cr and Ti-5Ni alloys

The hydrogen absorption and desorption kinetics and the p-C-T relationships of Ti, Ti-5Cr(at.%) and Ti-5Ni(at.%) alloys have been studied in the temperature range of 880 to 1050 K and in the pressure range of 1.3 to 13.3 kPa. The relative partial molar enthalpies for hydrogen solution in beta phase obtained from the p-C-T relationships are found to be - 71.0, - 68.3 and - 59.7 kJ/mol for Ti, Ti-5Cr and Ti-5Ni alloys, respectively. The constant volume method of the reaction rate analysis is used to determine the rate constants for hydrogen absorption and desorption. The activation energies for hydrogen absorption by Ti, Ti-5Cr and Ti-5Ni alloys are 110.1, 91.0 and 89.5 kJ/mol, respectively. The activation energies for hydrogen desorption are 67.0 and 61.8 kJ/mol for Ti and Ti-5Cr alloys, respectively. The hydrogen absorption is controlled by the alpha/beta phase interface process, whereas the rate controlling step for desorption is the hydrogen transport through the surface oxide film. (C) 1999 Elsevier Science S.A. All rights reserved.