Nanoindentation study on the characteristic of shear transformation zone in a Pd-based bulk metallic glass during serrated flow

Highlights: • A novel method was proposed to estimate the volume of shear transformation zone (STZ) in bulk metallic glass through statistical analysis of the serration behavior in nanoindentation. • It was found that the STZ size exhibits an increasing trend during nanoindentation. • The STZ activation can promote the formation of self-organized critical (SOC) phenomena during serrated flow. - Abstract: This paper presents the research on the evolution of shear transformation zone (STZ) in a Pd-based bulk metallic glass (BMG) during serrated flow under nanoindentation. A novel method of estimating the STZ volume through statistical analysis of the serrated flow behavior was proposed for the first time. Based on the proposed method, the STZ volume of the studied BMG at various peak loads have been systematically investigated. The results indicate that the measured STZ volumes are in good agreement with that documented in literature, and the STZ size exhibits an increasing trend during indentation. Moreover, the correlation between the serrated flow dynamics and the STZ activation has also been evaluated. It is found that the STZ activation can promote the formation of self-organized critical (SOC) state during serrated flow.