Abstract Structural changes in α-Al 2O 3 crystals implanted by 48Ti and 90Zr and subjected to thermal annealing have been investigated using ion scattering/channeling techniques. For the case of Ti implantation, the implanted species exhibits substitutionality in the as-implanted condition and undergoes anisotropic diffusion along the 〈0001〉 axis at a temperature of 1200°C which gives rise to the formation of needle-like precipitates partially coherent along the 〈0001〉 direction. For the case of Zr implantation, recovery of lattice damage begins in the Al sublattice at ∼ 800°C and in the O sublattice at ∼ 1300°C. Zr is not observed to be substitutional even after annealing to temperature of 1600°C. Results on the structural changes are correlated with measured mechanical property changes for the case of Cr, Ti, and Zr implanted into Al 2O 3 and thermally annealed to temperatures of 1600°C.