Effect of microstructure on the fracture behavior of micro–nano ZTA composite

Abstract

The microstructural effect on the crack propagation was investigated using two kinds of micro–nano ZTA composites made of micro-Al 2O 3 and nano-ZrO 2 particles. The results indicated that with low ZrO 2 content (10 vol.%) in the composite the presence of both large ZrO 2 particles located along Al 2O 3 grain boundary and very fine ZrO 2 particles embedded inside of Al 2O 3 grains was responsible for the appearance of transgranular fracture. Consequently, the composite showed a typical R-curve of rising up more quickly and better toughness than the composite with high ZrO 2 content (20 vol.%). The crack propagation inside of Al 2O 3 grains, depending on the nature of residual stress produced due to the thermal mismatch of Al 2O 3 and ZrO 2 as well as the phase transformation of ZrO 2 from tetragonal to monoclinic, was found to be in the way of either bypassing or splitting ZrO 2 particles.