An atomistic simulation study on ductility of amorphous aluminum oxide

Aluminum oxide is a widely recognized structural ceramic material known for electrical insulation and wear/corrosion resistance. Recent studies have challenged the conventional perception of brittleness by uncovering remarkable plasticity in amorphous aluminum oxides. To further enhance the fracture toughness of aluminum oxides and expand their applications in fields requiring resistance, it is crucial to analyze the factors influencing the tensile deformation process and investigate the underlying origins of ductility. In this study, molecular dynamics simulations were employed to compare the ductility of amorphous aluminum oxides with crystalline aluminum oxides and other amorphous ceramic oxides. Our findings indicate that the degree of crystallinity significantly influences ductility. Moreover, the simulations revealed that amorphous aluminum oxides exhibit the highest total elongation among binary structural ceramic oxides such as TiO ₂ and SiO ₂, underscoring the intrinsic plasticity of aluminum oxide. Furthermore, we discovered that aluminum oxides possess a low bond-dissociation energy (E _BD ) compared to other structural ceramic oxides, leading to a higher occurrence frequency of plastic deformation mechanisms. Based on these observations, low E _BD could be proposed as the probable indicator that enables the estimation of ductility of structural amorphous oxides without resorting to complex atomistic simulations. This quantitative criterion, based on an easily accessible material property, provides valuable guidance for predicting the ductility of newly-designed structural ceramic materials.