Nanocrystalline coating enhanced ductility in a Zr-based bulk metallic glass

Compression tests were conducted on the as-cast Zr₅₈Ni_13.6Cu₁₈Al_10.4 metallic glass at room temperature. The effect of nanocrystalline Ni-15%Fe coating (mean grain size: ∼10 nm) on mechanical properties was investigated. The results demonstrate that the strength, elastic limit, Young’s modulus, and fracture geometry and morphology are not affected by this nanostructured coating. However, the compressive plastic strain increased noticeably when the specimens were coated with a layer of nanocrystal, which is attributed to the increased shear band density. The high shear band density is suggested to be due to the inhibition of shear band operation by nanocrystalline coating. The significance of this study is that a new strategy was developed to improve the ductility of bulk metallic glasses.