Enhanced plasticity by nanocrystallite in bulk amorphous Al2O3-ZrO2-Y2O3

Ceramics are hard and brittle due to the complex crystalline structure, and the plastic deformation in amorphous oxides at moderate temperature may provide new ideas for achieving plasticity in ceramic materials. In this article, deformations in bulk amorphous Al2O3-ZrO2-Y2O3 precipitated with different amounts of nanocrystallite were investigated under moderate temperature compression. Almost no plastic deformation occurred in fully amorphous AZY at 500 °C; however, a large plastic strain of 10.5% was achieved in sample with 3.65 mol% nanocrystallite, and the plasticity degraded as the crystallinity increased to 24.80 mol%. Plasticity enhanced by nanocrystallite in bulk amorphous oxides was achieved at temperature as low as 500 °C, and the deformation exhibited an unusual behavior of brittle-plastic-brittle transition with increasing crystallinity. The plastic strain was mainly resulted from shear banding along with further densification, and shear banding was confirmed as the dominating mechanism. Shear banding as well as the brittle-plastic-brittle transition was explained in terms of free volume theory. This work might provide a profound understand of plastic deformation and shear banding in bulk amorphous oxides, and inspire new methods to improve plasticity in amorphous materials.