Grain size dependence, mechanical properties and surface nanoeutectic modification of Al ₂ O ₃ -ZrO ₂ ceramic

The present work aims to provide fundamental insights into the grain size dependence and mechanical behavior of hot-pressed Al ₂ O ₃ -ZrO ₂ ceramic at its eutectic composition, and further to explore the hardening effect of laser-induced surface nanoeutectic layer. The underlying correlations between densification behavior, grain size distribution and mechanical properties were elucidated. Sintering at 1550 °C promotes the densification without extensive grain growth, and in this case the sample exhibits a critical density of 99.3 %. The average grain size is tailored into a range of 0.6–0.9 μm, and the measured flexural strength and toughness reach 1100 MPa and 11 MPa·m ^1/2 , respectively. The metastable t-ZrO ₂ grains indeed play a pivotal role in energy dissipation at the crack tip through crack deflection and branching. In addition, the mechanical behavior is reasonably explained through constructing a multilevel toughening mechanism map associated with grain size distribution of ZrO ₂ . Particularly, surface nanocrystallized Al ₂ O ₃ -ZrO ₂ eutectic layer with a thickness of 1000 μm free of pores and cracks is achieved by a rapid laser melting process. The outmost laser-modified nanoeutectic layer exhibits a fine cellular structure with an interphase spacing of only 105 nm and a hardness of as high as 26.1 GPa, which provides a promising potential in enhancing significantly the hardness and wear resistance for applications as sliding ceramic components.