Insights into intragranular precipitation and strengthening effect in Al2O3/SmAlO3 ceramic with eutectic composition

This work concerns the microstructure-mechanical properties relationship in Al2O3/SmAlO3 composites prepared by hot pressing at temperatures from 1450 °C to 1650 °C. Dense samples have been prepared using co-precipitated trigonal α-Al2O3 and orthorhombic SmAlO3 at the pseudo-binary eutectic composition. The overall microstructure coarsens with increasing processing temperature, but the nanoscale precipitates within α-Al2O3 and SmAlO3 grains contribute to coherency strains and distortions in Al2O3/SmAlO3 prepared at 1650 °C. The intragranular SmAlO3 precipitates in Al2O3 grains exhibit semi-coherent interface and an orientation relationship of the intragranular phase SmAlO3 and alumina matrix close to two different zone axes, namely [23¯1]SmAlO3 and [4¯401]Al2O3. Consequently, significant strengthening effect is found from the measured hardness values on the sample sintered at 1650 °C. The measured flexural strength and single edged notched beam fracture toughness of the Al2O3/SmAlO3 ceramic are comparable to traditional secondary phases reinforced alumina composites. The sample sintered at 1500 °C exhibits a flexural strength of 558 MPa and a fracture toughness of 5.59 MPa⋅m1/2.