Microstructure and high-temperature deformation behavior of Al2O3–TiO2 obtained from ultra-high-pressure densification of metastable powders Original Research Article

Metastable alumina composite powders with 13 wt.% titania were produced by plasma spraying using liquid nitrogen quenched substrates. The material consisted of a mixture of Al2O3 in a distorted spinel structure and a large amount of amorphous phases. High-pressure–high-temperature sintering below the crystallization temperature of the amorphous phase yielded a crystalline/amorphous composite that was used for creep experiments. During heating to the desired testing temperature, crystallization occurred and an in situ composite composed of corundum and rutile was obtained. This material exhibited superior deformation behavior compared to conventionally processed alumina materials. Comparably low temperatures of 1100 °C could be utilized to achieve plastic deformation of the material under a pressure of 50 MPa. Coble grain boundary creep with n = 1 and a low activation energy for diffusion of 390 kJ mol−1 was assumed to be the deformation mechanism.