Reactions of hydrogen with V-Cr-Ti alloys

The interest in vanadium alloys for use as a first-wall material in fusion reactor applications has led to a study to determine the effects of hydroge n on the mechanical properties of certain V-Cr-Ti alloys. Hydrogen uptake b y the alloys is a function of temperature and pressure. In the absence of i ncreases in oxygen concentration, additions of up to 400 wpm hydrogen to V- 4Cr-4Ti did not result in any significant embrittlement. However, when hydr ogen approached 500 wppm, rapid embrittlement occurred at 325 degrees C tha t was suggested to result from formation of a hydride phase upon cooling. W hen oxygen was added as well, either during or prior to hydrogen exposure, synergistic effects depending on grain size occurred that led to significan t embrittlement by 35-130 wppm hydrogen. Because of its synergism with hydr ogen and ubiquitous presence in most environments, oxygen pick-up remains a s one of the major concerns for use of V-Cr-Ti alloys in fusion reactor app lications. (C) 1999 Elsevier Science B.V. All rights reserved.