Nanoscale flaw tolerance behaviour of polycrystalline tetragonal zirconia nanopillars

Abstract

Flaw tolerance behaviour of polycrystalline tetragonal zirconia nanopillars under compression is investigated by completing a series of large-scale atomistic simulations. Our simulation results show that the observed tetragonal to monoclinic phase transformation in zirconia does not necessarily nucleate around a pre-existing defect. A competing mechanism between grain boundary (GB)-induced and void-induced phase transformation is revealed. This work is the first direct atomistic simulation of flaw tolerance behavior in shape memory ceramics that offers a pseudo Griffith relationship between the strength, void size, and average grain size. The key finding is that the mechanical properties, particularly the strength, can become insensitive to a pre-existing defect in certain conditions depending on the average grain size and defect size. The obtained results provide new insight into the deformation mechanisms of defective polycrystalline tetragonal zirconia nanopillars.