Cooperative effects of free volume and nanocrystallite on plastic deformation in bulk amorphous Al2O3–ZrO2–Y2O3

Abstract Bulk amorphous Al2O3–ZrO2–Y2O3 samples are fabricated by hot pressing and heat treated at 750–950 °C to adjust the free volume and crystallinity degrees, and the cooperative effects of free volume and nanocrystallite on plasticity are explored. With increasing heat treatment temperature, the free volume decreases monotonically, and the nanocrystallization initiates above 800 °C. Under compression at 500 °C, the plastic strain is in linear correlation to the free volume for fully amorphous samples or amorphous/nanocrystalline composites, respectively. The larger free volume concentration is beneficial to the formation and propagation of shear bands, and achieves to larger plasticity. Although the amorphous/nanocrystalline composites have lower free volume, they display better plasticity than the fully amorphous samples, attributed to the microstress concentration at the interfaces between nanocrystalline and amorphous matrix. Due to the coexistence of tiny nanocrystallite and sufficient free volume, the sample heat treated at 850 °C exhibits the best plasticity with strain of 9.9%.