Effects of hydrogen on the single-crystal elastic moduli of Nb-V and Nb-Ta solid solutions

The single-crystal elastic moduli of several Nb-V and Nb-Ta solid solutions were measured at 300K with, and without, an H or D interstitial solute. The intent was to determine whether the enhancement of the terminal solubility for H(D) in these alloys is related to any of the following properties: (a) absolute values of the C ij , (b) elastic anisotropy, (c) relaxation of the C' shear modulus caused by H or its isotopes, or (d) the increase in the C 44 shear modulus caused by solute H(D) and presumed to result from electron band shifts. The variations in C ij for the binary alloys of Nb-V suggest and atomic ordering that may be related to the H solubility. The magnitude of the effect of H on C 44 varies with alloy composition and may indicate that indicate that singularities in the electron band-structure of Nb are removed by adding V or Ta, thereby significantly changing the electronic effects of adding H.