Formation and densification behavior of reaction sintered alumina–20 wt.% aluminium titanate nano-composites

• The heat treatment schedule affects the aluminium titanate nucleation mechanisms.
• We determine the residual strain resulted from thermal expansion mismatch.
• We approve that the spontaneous microcracking cause to unusual density decrement.
• Results reveal that Al2TiO5 grains crack along the (010) crystallographic planes.

Densification and reaction sintering behavior of the alumina–20 wt.% aluminium titanate nano-composites were studied. Nano TiO2 powders were used in achieving the aluminium titanate phase during reaction sintering of alumina and titania. High resolution X-ray diffraction (HR-XRD) and scanning electron microscopy (SEM) results revealed that the aluminium titanate formation was affected by heating rate and soaking time at the elevated temperatures. The content of aluminium titanate phase decreased during increment of heating rate and increased during increment of soaking time at sintering temperature. Final densities of the sintered composites at 1550 °C were lower than those sintered at 1450 °C which can be explained by the grain cracking phenomenon induced by thermal expansion mismatch. The residual strain of the aluminium titanate grains released after grain cracking. The Al2TiO5 grains cracked along the (010) crystallographic planes because of the most positive expansion of the b-axis, and the lattice parameter b reverted to its original value after grain cracking.