Critical obstacle size to deflect shear banding in Zr-based bulk metallic glass composites

The Zr₅₃Cu₂₂Ni₉Al₈Ta₈ bulk metallic glass composite (BMGC) rods have been reported to present superior plastic strain up to 30% at room temperature. The remarkable plasticity is demonstrated to be contributed by the in-situ Ta-rich precipitates in micro-sized (10-20 micro-meter) plus nano-sized (5-15 nm) scales, homogeneously distributed in the amorphous matrix. These Ta-rich particles act as discrete obstacles, separating and restricting the highly localized shear-banding, avoiding catastrophic shear-through of the whole sample and dramatically enhancing plasticity, as compared with the ZrCuNiAl monolithic BMG. To explore the critical particle size that can effectively deflect the shear banding, the Zr-based BMGC rods were plastically deformed to different strain levels (3%-25%) before fracture for investigating the interaction between the Ta-rich particles (micro- and nano-sized) and shear banding. The results suggest that the critical size of single particle or particle cluster for deflecting the shear band is greater than 20 nm and less than 100 nm. The best estimation suggests about 80 ± 20 nm.