Anomalous decrease of propagation rate of the macroscopic shear band in the Zr-based bulk metallic glasses at temperatures 170 and 77 K

Abstract

The plastic deformation and fracture of cylindrical samples of the bulk metallic glasses Zr 62Cu 15.5Ni 12.5Al 10 and Zr 64.13Cu 15.75Ni 10.12Al 10 have been studied in uniaxial compression in the temperature range 300–4.2 K. At the temperature 300 K the deformation curve has serrated (jump-like) type, caused by the propagation of narrow shear bands. At the deformation level of approximately 3–4% the catastrophic, uncontrolled failure of the specimens occurs resulting from propagation of the macroscopic shear band with a rate ∼10 3 m/s, which is comparable with the sound velocity. A decrease of the temperature from 300 K down to 170 and 77 K changes the type of deformation curves from a jump-like to a smooth one. An interesting low temperature anomaly of deformation process was found: “slow” (with a rate of approximately 10 −6 m/s) propagation of a single macroscopic shear band is observed at 170 and 77 K. When the samples are cooled to 4.2 K their macroscopic plasticity vanishes, and they undergo fracture, just as at 300 K, as a result of the propagation of the catastrophic shear band with nearly sound speed.