Low-temperature elastic constant Cij (T) measurements for Cu60 Zr30 Ti10 and Cu60 Hf25 Ti15 bulk metallic glasses (BMGs) have been carried out to clarify their acoustic properties including a nonlinear interaction term. The BMGs show remarkably low shear to bulk modulus ratio C44 B or equivalently high Poisson's ratio ν compared with the corresponding crystalline states. The Cij (T) behaviors are well described by Varshni's formula and estimated Einstein temperatures suggested significant softening in the transverse-mode acoustic phonon. Mean Grüneisen parameters γ derived from dBdT slopes become almost identical with those of crystalline Cu. Our theoretical analysis based on inhomogeneous microstructure model successively explains the elastic constants and characteristic features of the BMGs within a framework of quasiharmonic thermodynamics, suggesting that microstructural inhomogeneity plays a dominant role in the BMGs.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 2007 Sept 28