Grain size dependence of fracture toughness for fine grained alumina

The fracture toughness of a series of fully dense polycrystalline alumina samples prepared by electrical field assisted sintering with grain sizes varying from ∼290 nm to ∼3.3 μm was measured using the surface crack in flexure method. Fracture toughness values for different grain sizes were statistically analyzed based on the Weibull distribution. It was found that the fracture toughness in fine grained alumina is independent of grain size. The characteristic fracture toughness calculated from the Weibull distribution is 3.37 MPa m1/2.

► Fully dense fine grained aluminas with grain size from 290 nm to 3.3 μm were obtained. ► Fracture toughness values with different grain sizes were statistically analyzed. ► Fracture toughness in fine grained alumina is independent of grain size. ► Characteristic fracture toughness in fine grained alumina is 3.37 MPa m1/2.