Hydrogen internal friction peak and thermal desorption spectrum in amorphous Cu50Zr50

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The hydrogen internal friction (HIF) peak and hydrogen thermal desorption spectrum in amorphous Cu 50 Zr 50 (a-Cu 50 Zr 50 ) were investigated for hydrogen concentrations C H below about 50 at.%. Features of the HIF peak very similar to those in a-Cu 50 Ti 50 were obtained here, i.e . S t ∝ N ( μ ) and n ( E ; μ ) were composed of seven constituent gaussian distributions in E where S t denotes the total relaxation strength of the HIF peak, N ( G ) the site energy G distribution for hydrogen atoms where G is the free energy of occupation of a site, n ( E ; μ ) the activation energy E distribution in N ( μ ) and μ the chemical potential of hydrogen in the specimen. N ( G ) appeared to consist of the gaussian distributions N 1 ( G ) for C H ⩽ 16 at .%, N 2 ( G ) for 16 at .% ⩽ C H ≲ 35 at .% and N 3 ( G ) for 30 at .% ≲ C H . We surmised N 1 ( G ), N 2 ( G ) and N 3 ( G ) to correspond to the 4Zr, 3Zr + 1Cu and 2Zr + 2Cu sites respectively. From the thermal desorption spectra, g ∗ − G ≈ 0.7 eV (H atom) −1 near the bottom of N 3 ( G ) and g ∗ − G ⩾ 1.0 eV (H atom) −1 for N 2 ( G ) were estimated, where g ∗ denotes the energy of the transient state for the formation of an H 2 molecule at the specimen surface. The close similarity of the HIF peaks found in a-Cu 50 Zr 50 and a-Cu 50 Ti 50 suggests that these features reflect the common properties of amorphous alloys of an early transition metal with a later transition metal and that the model proposed for the HIF peak in a-Cu 50 Ti 50 might apply to a-Cu 50 Zr 50 .