HYDROGEN INTERNAL-FRICTION PEAK IN AMORPHOUS CU50TI50

Effects of annealing at 423 K and deformation on the hydrogen internal friction peak (the H-peak) in the H-concentration, C(H), below 32 at%, and the thermal desorption spectrum, TDS, for C(H) below 46 at% are investigated on amorphous Cu50Ti50 (a-CuTi). The results for the H-peak suggest the following: in a-CuTi, only H-atoms occupying the interstitial sites with G equal sign with dot above and below mu in N(G) can contribute to the H-peak, where N(G) denotes the site energy, G, distribution and mu the chemical potential of the H-atoms in the specimen. N(G) is composed of Gaussian distributions N1(G) for C(H) less-than-or-equal-to 12 at%, N2(G) for 9 less-than-or-equal-to C(H) less-than-or-equal-to 35 at%, and N3(G) for C(H) greater-than-or-equal-to 28 at%. N1(G) to N3(G) are surmised to correspond to the 4 Ti, 3 Ti + 1 Cu, and 2 Ti + 2 Cu tetrahedral sites, respectively. From these results combining with the near-neighbor blocking model for the H occupation, it is surmised that in a-CuTi, the H-peak is associated with H atoms within the rather large clusters of the tetrahedra of the same chemical composition. From TDS, g* - G3,0 less-than-or-simular-to 0.5 eV/H-atom, g* - G2,0 greater-than-or-simular-to 0.8 eV/H-atom, and g* - G1,0 > g* - G2,0 are estimated, where G(i),0 denotes the mean, G, for N(i)(G), g* the transient state to form a H2-molecule at the specimen surface. The H-peak profile reflects an activation energy (E) distribution n(E; mu) in N(mu). For all N(i)(G), n(i)(E; G) in N(i)(G) is composed of six constituent Gaussian distributions CGD's. Annealing and deformation do not change the outlines for N(i)(G) and n(i)(E; G) except that annealing often causes a strong increase of the H-peak as a whole for 6 less-than-or-equal-to C(H) less-than-or-equal-to 14 at% which appears to be canceled by subsequent deformation. For CGD's, annealing gives rise to the complementary increase in CGD-1 and decrease in CGD-2 for C(H) at around 7 at% which remains unchanged after subsequent deformation. These results suggest that the as-prepared state is different from the deformed state.