The volume of a quenched glassy alloy is a variable of cooling rates during the amorphization. Hence a change in the volume caused by the structural relaxation can be regarded as a degree of amorphousness. The density of Zr 50 Cu 40 Al 10 bulk glassy alloys (BGAs) increases linearly with the annealing temperature below the glass-transition temperature (T g ). With increasing the annealing temperature, the tensile strength and Vickers hardness show constant values, whereas the Young's moduli and Charpy impact values become larger and smaller, respectively. Especially, Charpy impact values of Zr-Cu-Al BGAs have a linear relationship with the relative value of excessive free volume, which correspond to the volume-change ratio caused by the full structural relaxation.

We examined relaxation and crystallization behavior of the ternary Zr 50 Cu 40 Al 10 metallic glass by using positron annihilation and transmission electron microscopy (TEM). Observed changes in positron annihilation lifetime of the alloy annealed isothermally at 673 K, which is below the glass transition temperature, correlate well with observed density changes; while coincidence Doppler broadening (CDB) spectra exhibit no significant change. These observations demonstrate that free volume decreases without a rearrangement of atoms during structural relaxation. On the other hand, CDB spectrum has exhibited considerable changes when the same alloy was annealed at 773 K. TEM observations suggested that crystallization occurs via growth of spherulites of several hundred nm in diameter, which themselves are composed of radially grown grains. Chemical analysis revealed that Cu atoms are partitioned out during the growth of the spherulites. Diffraction study indicated that the unit cell of the crystalline phase belong to an orthorhombic system with a ¼ 0:892, b ¼ 0:550, and c ¼ 1:060 nm; while remaining interspherulite regions are found to crystallize into an fcc phase with a ¼ 1:28 nm, which is probably isostructural to the 3 phase.

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In order to examine mechanical properties of a metallic glass Zr50Cu40Al10 in low temperature below room temperature, the temperature T dependence of mechanical resonance of ultrasonic wave are measured. The mechanical resonance frequency in an as-quenched sample shows an abrupt increase at 200K for longitudinal wave and 160 K for transverse wave with decreasing T. After this abrupt increase, the sound propagation cannot be detected below these temperatures but the wave propagation is restored with increasing T and there is an abrupt decrease at 260K for the both wave modes. The similar hysteresis is observed in temperature dependence of the electrical resistivity. These suggest a kind of structure instability of Zr50Cu40Al10 in low temperature region.