M. Quintard

The α peak in cold-worked and hydrogen-loaded niobium

Some experiments performed in an inverted torsion pendulum (90 to 300/sup 0/K, 1 and 15 Hz) on niobium in the form of marz-grade polycrystalline rods (3.18 mm in diameter). The niobium was first annealed at 2000/sup 0/K in an uhv system (10/sup -5/ Pa) for about 3 h. A bamboo structure was obtained after this treatment, and degassing was confirmed by the absence of any detectable Snoek peak (oxygen, carbon or nitrogen), and by the low macroscopic tensile yield stress at room temperature (approximately or asymptotic to 10 MPa). The internal friction spectra of this material as a function of plastic deformation was determined.

An Analysis of the α Peak in Niobium and Vanadium by Means of the Schoeck Theory

ABSTRACT The internal friction of deformed and hydrogenated niobium and vanadium was measured between 90 and 300 K, both in the cycle and kilocycle frequency range. The α peak was enhanced by hydrogen charging, and a pronounced asymmetry in the peak shape was observed in the cycle range. It is thought that the α peak is a cold-work peak (Snoek-Koster peak) resulting from the viscous dragging of hydrogen in the strain field of moving dislocations. The Schoeck model is shown to be a suitable tool for analysing the peak structure by means of the temperature dependence of the relaxation parameters expected from this model.