In literature, alumina-zirconia composites have been extensively studied, and it is recognized that the addition of zirconia can be beneficial in terms of mechanical properties. Depending on the phase in which the zirconia is, the particle size or the presence or absence of stabilizer for the tetragonal phase, different strengthening mechanisms can be involved, such as stress-induced phase transformation , interaction of cracks with microcracks in the zirconia or residual stresses induced by differential thermal expansion between zirconia and alumina . In this work, we note a strengthening with zirconia, but only when it is in the tetragonal phase.