Superplastic nanocrystalline ceramics at room temperature and high strain rates

Tensile-loading molecular dynamics simulations show that nanocrystalline SiC not only becomes ductile, but can be superplastically deformed at room temperature when grain sizes are reduced to d ∼ 2 nm. The calculated strain rate sensitivity, 0.67, implies a superplastic ceramic able to attain strains of up to 1000% at room temperature and typical strain rates (∼10^-2 s^-1). The origin of the superplasticity is linked to an unusually steep rise in creep rate to 10⁶ s^-1 for d = 2 nm. The results explain recent observations in SiC nanowires and suggest novel opportunities for structural ceramics.