Mechanical behavior of tetragonal zirconia nanopillars subjected to uniaxial loading: A molecular dynamics study

Abstract

A novel stress-strain relation with two stages of linear elastic deformation is observed in [001]-oriented tetragonal zirconia nanopillars subjected to tensile loading via molecular dynamics simulation. This phenomenon results from a phase transformation from the tetragonal structure to the monoclinic one. Detailed explorations including the crystallographic structural analysis and the atomic strain calculation have been made to further elucidate the stress-strain curve. The lattice orientation strongly affects the plastic deformation mechanism, i.e., the [001]- and [011]-oriented nanopillars experience the phase transformation under tensile loading, while the brittle fracture is induced for the orientation lying along the [111] direction. Complementary uniaxial compressive tests are performed to study the loading direction dependence. The deformation mechanism differs for the nanopillars with the same lattice orientation but different loading directions; for instance, under compressive loading, the plastic deformation behavior for [001]-oriented nanopillar is governed by intense dislocation activity rather than phase transformation. Additionally, a significant temperature effect is observed, with Young's modulus decreasing linearly from 323.97 to 283.55 GPa as the temperature increases from 300 to 1400 K. This work will help deepen the understanding of the tetragonal-to-monoclinic transformation and nanoscale mechanical behavior of zirconia.