Elastic properties of Cu-based bulk metallic glass around glass transition temperature

Temperature dependent elastic constants C_ij(T) of Cu ₆₀Hf₃₀Ti₁₀ bulk metallic glass (BMG) have been investigated in a MHz frequency range using electromagnetic acoustic resonance (EMAR) up to 823 K. At room temperature, the BMG showed high Poisson's ratio v arising from low shear modulus G compared with that of constitutive crystalline elements. With increasing temperature, G showed usual linear temperature dependence while it suddenly drops around glass transition temperature, T _g. Within a framework of quasiharmonic approximation, Grüneisen parameter γ around T_g is estimated to be 10. This extremely large γ indicates the high anhramonicity of long wavelength limit acoustic mode phonon in the supercooled liquid state. The unusual elastic behavior can be interpreted on the basis of heterogeneous microstructure.