Modelling of nanoindentation behaviour in MgO doped alumina

Here we report the modelling of the nanoindentation behaviour of 1-5 wt% MgO doped alumina ceramics. It is well-known that the nanoindetation technique is highly efficient in digging out the mechanical properties of various materials including ceramics especially, at small length scale. The samples prepared by the pressureless sintering technique are characterized by the x-ray diffraction, field emission scanning electron microscopy and the nanoindentation techniques. The experimental results obtained from the nanoindentation experiments exhibit a unique nanoindentation size effect as well as the occurrences of localized plasticity events. This unique observation is what drives the inspiration for modelling such behaviours. The modelling of this nanoindentation size effect identifies that it could be linked to the load dependent spatial variations in both the dislocation loop interaction zone size and the deformation resistance. The localized plasticity events are found to happen due to the simultaneous contributions from dislocation nucleation, localized shear deformation bands formation and microcracking formations. The critical loads at which localized plasticity events are initiated increase with the amount of MgO. It happens due to the simultaneous enhancements in the relative density, spinel phase, relative amount of fine grains, and decrease in average size of the fine grains. The implications of these observations for microstructural design of structural ceramics like alumina with enhanced contact deformation resistance at the nanoscale are also discussed