Performance of V-Cr-Ti alloys in a hydrogen environment

A systematic study is underway at Argonne National Laboratory to evaluate t he mechanical properties of several V-Cr-Ti alloys after exposure to enviro nments containing hydrogen at various partial pressures (pH(2)). The goal i s to correlate the chemistry of the exposure environment with hydrogen upta ke by the samples and with the resulting influence on microstructures and t ensile properties of the alloys. Other variables examined are specimen cool ing rate and synergistic effects, if any, of oxygen and hydrogen on tensile behavior of the alloys. Experiments were conducted to evaluate the effect of pH(2) in the range of 3 x 10(-6) and 1 Torr on tensile properties of two V-Cr-Ti alloys. Up to pH(2) of 0.05 Torr, negligible effect of H was obser ved on either maximum engineering stress or uniform and total elongation. H owever, uniform and total elongation decreased substantially when the alloy s were exposed at 500 degreesC to 1.0 Torr of H-2 pressure. Preliminary dat a from sequential exposures of the materials to low-pO(2) and several low-p H(2) environments did not reveal adverse effects on the maximum engineering stress or on uniform and total elongation when the alloy contained approxi mate to 2000 wppm O and 16 wppm H. Furthermore, tests in H-2-exposed specim ens, initially annealed at various temperatures, showed that grain-size var iation by a factor of approximate to2 had little or no effect on tensile pr operties. Also, specimen cooling rate had a small effect, if any, on the te nsile properties of the alloy. (C) 2000 Elsevier Science B.V. All rights re served.