The ballistic impact performance of nanocrystalline zirconia-toughened alumina (nZTA) and alumina ceramics

The ballistic impact performance of nanocrystalline zirconia-toughened alumina (nZTA) ceramics, comprising 15 wt% nano-yttria-stabilised zirconia in a sub-micron alumina matrix, have been studied through depth of penetration tests and compared to the results for monolithic alumina. The penetration resistance of each material was evaluated by fitting the penetration depth results against the thickness of the ceramic targets. These results show that, despite micro-Raman analysis of the nZTA confirming the occurrence of the classic tetragonal-to-monoclinic zirconia phase transformation, nZTA ceramics provide no benefit with respects to penetration resistance compared to monolithic alumina. Analysis of the fragments generated using Cr3+/Al2O3 fluorescence spectroscopy shows that both the nZTA and alumina experience similar amounts of plastic deformation as a function of fragment size, with finer fragments (<150 µm) exhibiting more plastic deformation than coarser fragments (>150 µm). These results are validated through fracture surface observations and subsurface dislocation analysis using SEM and TEM respectively.