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

Abstract 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 Al 2 O 3 :ZrO 2 :MgAl 2 O 4 (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 Al 2 O 3 and MgAl 2 O 4 grains, and the smaller grains (100–300 nm in diameter) are primarily ZrO 2 . 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. ZrO 2 grains, and some of the large grains, i.e. MgAl 2 O 4 grains. We observed both plastic and elastic deformations in different sample regions in these multi-phase ceramic nanocomposites at room temperature.