Ultrasonic measurements of elastic properties are traditional for studying structural transitions in metallic glasses. In last few years glassy state was obtained for massive specimens of a new generation of multicomponent alloys - bulk metallic glass (BMG) of Pd-Ni-Cu-P and Zr-Ti-Cu-Ni-Be systems.
We have applied the microacoustical technique for measuring local elastic properties and imaging internal microstructure of BMG samples. Short probing pulses of focused high-frequency ultrasound penetrate into the specimen as convergent beams of longitudinal and transverse waves. Echo pulses caused by reflection at the specimen face and backside are employed for measuring local values of sound velocities, both longitudinal and transverse ones. Echo signals reflected from details inside the specimen are employed for imaging its bulk microstructure.
The BMG specimens were produced by the quenching method. Different states (glassy state, super-cooled liquid (SCL) and crystallized states) were obtained by annealing of the samples under normal and high pressure and at different temperatures near the glass transition and onset crystallization. Local values of longitudinal and transverse wave velocities and local elastic properties (bulk and shear moduli; Poisson coefficient) have been measured for an as-quenching specimen and for samples annealed at different temperature. Decreasing the longitudinal wave velocity (~6%) and bulk elastic modulus (~20%) has been observed in transition from the glassy state to SCL. High attenuation was observed in the crystallized BMG sample. Acoustic images (C-scans) evidence that course grain microstructure is inherent to BMG sample at this state.

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