Nanoindentation of single-crystal and polycrystalline yttria-stabilized zirconia: A comparative study by experiments and molecular dynamics simulations

Abstract

A combination of nanoindentation experiments and molecular dynamics (MD) nanoindentation simulations is carried out in this paper to study the mechanical properties and deformation behaviors of single-crystal and polycrystalline yttria-stabilized zirconia (YSZ). Different Young’s moduli are found in the nanoindentation experiments of single-crystal and polycrystalline YSZ samples, though these two YSZ materials almost have the same hardness. In addition, with the aid of atomic force microscopy, different deformation behaviors are observed in single-crystal and polycrystalline YSZ. The different Young’s moduli and deformation behaviors of single-crystal and polycrystalline YSZ observed in experiments are explained by MD simulations. The simulation results show that during the indentation process, the slip occurs inside single-crystal YSZ but along the grain boundaries of polycrystalline YSZ. These different deformation mechanisms between single-crystal and polycrystalline YSZ account for the lager Young’s modulus and more significant pile-up phenomenon observed in single-crystal YSZ. In addition, our MD simulations also reveal that the mechanical properties of YSZ are almost independent of the temperature but can be significantly affected by the number of YSZ grains. Specifically, both the Young’s modulus and hardness of polycrystalline YSZ are found to decrease as the number of grains grows.