Mg-based bulk metallic glass under tension test or compression test will show significant brittleness in macroscope, leading to the difficult to study the plastic deformation behavior. With high spatial and temporal resolution instrumented nanoindentation, an experimental investigation into the serrated flow that is created during the plastic deformation at different loading rate was conducted. The results showed that low loading rate promote conspicuous pop-in events and high loading rate suppress pop-in behavior. The reason is that a single shear band is sufficient to render the plastic strain at low loading rate but multiple shear bands is required at high loading rate. To gain a better understanding of the mechanism despite the characteristic lack of periodicity in the intermittent pop-in events. Ergodically processing is introduced to demonstrate the statistic distributions of the strain burst size. The results showed that the smaller strain bursts are more probable and follow a power-law distribution and the exponent is constant about 1.45 at all experimental loading rates. For a given loading rate, with increasing the strain burst size, the distributions of the strain burst sizes do not follow a power-law distribution but decrease exponentially in probability. Finally, based on the strain rate sensitivity of hardness, we estimated the volume of the shear transformation zone.
Keywords: Metallic glass; Nanoindentation; Strain bursts; Ergodically processing; Strain rate sensitivity; shear transformation zone