Nanolaminates Utilizing Size-Dependent Homogeneous Plasticity of Metallic Glasses

Abstract

Homogeneous plasticity in metallic glasses is generally only observed at high temperatures or in very small structures (less than approximate to 100 nm), so their applications for structural performance have been very limited. Here, nanolaminates with alternating layers of Cu50Zr50 metallic glass and nanocrystalline Cu are synthesized and it is found that samples with an optimal composition of 112-nm-thick metallic-glass layers and 16-nm-thick Cu layers demonstrate a maximum strength of 2.513 GPa, a value 33% greater than that predicted by the rule-of-mixtures and 25% better than that of pure Cu50Zr50 metallic glass. Furthermore, approximate to 4% strain at fracture is achieved, suppressing the instantaneous catastrophic failure often associated with metallic glasses. It is postulated that this favorable combination of high strength and deformability is caused by the size-dependent deformation-mode transition in metallic glasses, from highly localized plasticity, leading to immediate failure in larger samples to homogeneous extension in the smaller ones.