Size- and stability-dependent fracture scaling in nanoscale metallic glass

Abstract

Experiments show a significant size effect in the fracture modes of the metallic glass (MG) nanowires, while simulations often diverge due to differences in thermal histories caused by timescale issue of the classical molecular dynamics quenching methods. This leads to disparities between computational and experimental results. To address this, we used a hybrid molecular dynamics (MD) and Monte Carlo thermal cycling method to fabricate well-annealed MG nanowires with effective quenching rates significantly lower than those of MD-prepared samples. Our findings reveal that fracture mode transitions are strongly tied to thermal history. For high quenching rate samples, the fracture mode is only dictated by the aspect ratio (L/D) of nanowires, aligning with existing simulations. For low quenching rate samples, the critical factor determining fracture is the diameter (D), matching experimental observations. This resolves the discrepancies between simulations and experiments on size-dependent fractures in nanoscale MGs. Microscopic analysis links this variation to the intrinsic plastic zone width (δ₀), influenced by the aspect ratio in high rates but correlated solely with diameter in low rates. We propose a universal model for fracture scaling with size and thermal stability in nanostructured MGs.