Faceting, Grain Growth, and Crack Healing in Alumina

Reactive molecular dynamics simulations are performed to study self-healing of cracks in Al2O3 containing core/shell SiC/SiO2 nanoparticles. These simulations are carried out in a precracked Al2O3 under mode 1 strain at 1426 degrees C. The nanoparticles are embedded ahead of the precrack in the Al2O3 matrix. When the crack begins to propagate at a strain of 2%, the nanoparticles closest to the advancing crack distort to create nanochannels through which silica flows toward the crack and stops its growth. At this strain, the Al2O3 matrix at the interface of SiC/SiO2 nanoparticles forms facets along the prismatic (A) <(2) over bar 110 > and prismatic (M) <(1) over bar 010 > planes. These facets act as nucleation sites for the growth of multiple secondary amorphous grains in the Al2O3 matrix. These grains grow with an increase in the applied strain. Voids and nanocracks form in the grain boundaries but are again healed by diffusion of silica from the nanoparticles.