Grain and grain boundary activities observed in alumina–zirconia–magnesia spinel nanocomposites by in situ nanoindentation using transmission electron microscopy

At room temperature, in situ nanoindentation experiments in a transmission electron microscope reveal the grain and grain boundary activities in fully dense ceramic nanocomposites composed of Al2O3:ZrO2:MgAl2O4 (AZM) processed by spark plasma sintering (SPS). The composites have a bi-modal grain size distribution, where the larger grains (500 nm−1 μm in diameter) consist of Al2O3 and MgAl2O4 grains, and the smaller grains (100–300 nm in diameter) are primarily ZrO2. In situ dynamic deformation studies show that the AZM nanocomposites undergo the deformation mainly through the grain-boundary sliding and rotation of small grains, i.e. ZrO2 grains, and some of the large grains, i.e. MgAl2O4 grains. We observed both plastic and elastic deformations in different sample regions in these multi-phase ceramic nanocomposites at room temperature.