Ultrasonic properties of Cu ₄₅Zr _(45-x)Hf _xAg ₁₀ glassy alloys

Using ultrasonics, the acoustic characteristics of Cu ₄₅Zr _(45-x)Hf _xAg ₁₀ (x = 0-25) glassy alloys were examined in terms of complex elasticity. The values of bulk modulus (K), Lamè parameter (λ), Young's (E) and shear (G) moduli of Cu ₄₅Zr _(45-x)Hf _xAg ₁₀ glassy alloys are found to have a unique order for metallic materials, except for polymers. The large Poisson ratio (∼0.421) and the lower G/K ratio (∼0.167) at 25 at% Hf indicate rubbery characteristics that readily undergo uniaxial volume-preserving deformation but resist three-dimensional nonvolume-preserving deformation. The complex dynamic viscosity shows that visco-elasticity of the glassy alloys is dominated by shear motion. The large peaks in K and λ, and small ones in E and G at 5 at% Hf, and one large peak in the shear attenuation coefficient at 2.5 at% Hf, may indicate atomic morphological change by electron-transverse phonon coupling.