Influence of composition and plastic deformation on the hydrogen internal friction peak in amorphous Co-Zr alloys

Vibrating-reed measurements of the hydrogen internal friction peak were performed on a series of Co-Zr glasses ranging from Co55Zr45 to Co24Zr76. Variations in peak shape and growth behaviour (on increasing the H concentration) were observed for different alloy compositions, together with an increase of the average activation energy with cobalt concentration. These findings can be explained by the interstitial reorientation mechanism, assuming reorientation jumps of the H atoms between Zr4 tetrahedra; the activation energy increase then reflects the increase of the average Zr-Zr nearest neighbour distance with Co concentration known for this system. In Co55Zr45, two peaks were detected under certain H-charging conditions, possibly as a result of a chemical decomposition. After cold-rolling, additional IF peaks appear superimposed on the hydrogen peak (with large scatter), but can be distinguished as separate processes by a different annealing behaviour. (orig.)