The presence of interstitial carbon atoms was found to affect the hydrogenation properties of Ti25V35Cr40Cx (x = 0, 0.1, and 0.5) alloys over the range T= 30-300 degrees C. Heat treatment at T= 1200 degrees C was used to homogenize the distribution of carbon atoms throughout the specimens. X-ray diffraction, P-C isotherm curves, and thermodynamic measurements, including van't Hoff plots and in-situ temperature-programmed desorption spectra, were used to study the destabilization of the beta-phase monohydride and gamma-phase dihydride in annealed Ti25V35Cr40Cx as a result of the presence of interstitial carbon atoms. The experimental results showed that the interstitial carbon atoms introduced both obstacles and carbon-induced microstrain into the structure, which significantly destabilized the gamma-phase dihydrides to enhance the corresponding plateau pressures at T = 30-80 degrees C. On the other hand, destabilization of the beta-phase monohydride was less pronounced in the presence of interstitial C atoms at T = 150-300 degrees C. This effect was ascribed to a lower H content in the saturated beta-phase monohydrides as compared with the saturated gamma-phase dihydrides, as well as microstrain relaxation at higher temperatures. (C) 2014 Elsevier B.V. All rights reserved.