Plastically deforming ZrO2-SiO2 dual-phase nanocrystalline ceramics via dynamic hot forging and the associated microstructural changes.

Due to the intrinsic brittleness of ceramics, it is challenging to shape and plastically deform them. In this study, we plastically deformed ZrO 2 -SiO 2 dual-phase nanocrystalline ceramics (DPNCs) by an oscillatory pressure-assisted hot forging method, termed as "dynamic hot forging" (DHF). Under the synergistic effects of oscillatory pressure (60 ± 5 MPa, 2 Hz) and heat (1250 °C), significant dimensional changes of the DPNCs occurred after DHF. The as-sintered DPNCs consisted of tetragonal ZrO 2 nanocrystallites (NCs) embedded in an amorphous SiO 2 matrix. The forging process did not significantly alter the phase composition of the DPNCs, but obvious coarsening of ZrO 2 NCs occurred during DHF. Microstructural observations showed that the DPNCs deformed predominately through the viscous flow of amorphous SiO 2 at high temperature. No microcracks were observed although the DPNCs experienced large deformation. The morphology of ZrO 2 NCs did not significantly changed, i.e., they maintained a near-spherical morphology before and after forging. However, a large number of lattice defects in ZrO 2 NCs were formed due to forging, including edge dislocations, subgrain boundary, nanotwins, and stacking faults. The formation of lattice defects did not cause significant effect on the microhardness of the DPNCs. The results of this study suggest that DHF process is a promising technique to plastically deform and shape ceramics with crystalline-amorphous dual-phase microstructure. [ABSTRACT FROM AUTHOR]