Change of Site Occupancy of Hydrogen in Nb on Alloying with Undersized Mo

Abstract

The site occupancy of hydrogen in Nb–20 at.%Mo alloys is investigated at room temperature for H concentrations ( C H ) 2.6, 4.2, and 8.0 at.% by a channelling method using a nuclear reaction 1 H( 11 B, α)αα. Different from previous results for lower Mo concentrations, a large portion of H atoms are at tetrahedral ( T ) sites and, in addition, the octahedral ( O ) site occupancy is newly observed. The hydrogen distribution changes with C H . At C H =2.6 and 4.2 at.%, the 20–30% of H atoms are located at O sites, while at C H =8.0 at.% the fraction of the O -site occupancy remarkably decreases to 0–10%.