EFFECT OF ALLOY COMPOSITION AND TEMPERATURE ON HYSTERESIS IN (NB1-XFEX)1-XCRX-H SYSTEMS

The pressure-composition isotherms for the (Nb1-xFe(x))1-xCr(x)-H syst ems (where x = 0.05 and 0.07) were determined at three different tempe ratures, 298, 318 and 353K, using a Sieverts-type technique. Pronounce d hysteresis was observed. The pressure required for hydride formation , P(f), exceeded the decomposition pressure, P(d), by a factor of 20 a t room temperature. The (Nb1-xFe(x))1-xCr(x) alloys behave like most m etal-hydrogen systems in that as the temperature increases, the hyster esis effect decreases. The hysteresis effect is explained in terms of small radii of the solute (Fe and Cr) atoms which introduce strains in to the solvent (Nb) lattice.