Effect of Al 2 TiO 5 Content and Sintering Temperature on the Microstructure and Residual Stress of Al 2 O 3 -Al 2 TiO 5 Ceramic Composites.

A series of Al 2 O 3 -Al 2 TiO 5 ceramic composites with different Al 2 TiO 5 contents (10 and 40 vol.%) fabricated at different sintering temperatures (1450 and 1550 °C) was studied in the present work. The microstructure, crystallite structure, and through-thickness residual stress of these composites were investigated by scanning electron microscopy, X-ray diffraction, time-of-flight neutron diffraction, and Rietveld analysis. Lattice parameter variations and individual peak shifts were analyzed to calculate the mean phase stresses in the Al 2 O 3 matrix and Al 2 TiO 5 particulates as well as the peak-specific residual stresses for different hkl reflections of each phase. The results showed that the microstructure of the composites was affected by the Al 2 TiO 5 content and sintering temperature. Moreover, as the Al 2 TiO 5 grain size increased, microcracking occurred, resulting in decreased flexure strength. The sintering temperatures at 1450 and 1550 °C ensured the complete formation of Al 2 TiO 5 during the reaction sintering and the subsequent cooling of Al 2 O 3 -Al 2 TiO 5 composites. Some decomposition of AT occurred at the sintering temperature of 1550 °C. The mean phase residual stresses in Al 2 TiO 5 particulates are tensile, and those in the Al 2 O 3 matrix are compressive, with virtually flat through-thickness residual stress profiles in bulk samples. Owing to the thermal expansion anisotropy in the individual phase, the sign and magnitude of peak-specific residual stress values highly depend on individual hkl reflection. Both mean phase and peak-specific residual stresses were found to be dependent on the Al 2 TiO 5 content and sintering temperature of Al 2 O 3 -Al 2 TiO 5 composites, since the different developed microstructures can produce stress-relief microcracks. The present work is beneficial for developing Al 2 O 3 -Al 2 TiO 5 composites with controlled microstructure and residual stress, which are crucial for achieving the desired thermal and mechanical properties.