Nanoindentation study of yttria stabilized zirconia using molecular dynamics simulations*

Yttria stabilized zirconia (YSZ) is a versatile material with a wide range of applications due to its superior properties such as high mechanical strength, high dielectric constant, low thermal conductivity, and high chemical stability. However, its inherent brittleness presents challenges in the machining process. In order to improve YSZ's machinability, it is critical to understand its deformation and fracture mechanisms when it is subjected to external stress. The nanoindentation test is a popular experimental approach to study the hardness variation of materials and often serves as the first stage in studying a material's mechanical behaviors under loading. The current work studies YSZ's behaviors under nanoindentation tests with molecular dynamics (MD) simulations. During each test, a rigid indenter model is pushed into a cuboid YSZ substrate, and the contact force and hardness of the substrate during the test are analyzed. The simulations are carried out with various indentation speeds and temperatures as well as in different crystallographic orientations; the force and hardness dependence on these variables is investigated. Moreover, the effect of indenter shapes (spherical vs. Berkovich) is examined. It is observed that temperature and indentation speed have notable effects on the force and hardness profile, and depending on orientations of the substrate and indentation direction, the dominant deformation modes vary between the {111}<110> and {110}<101> slip systems.