Processing, microstructure and mechanical properties of 25 vol% YAG-Al2O3 nanocomposites

A co-precipitation method was investigated to manufacture 25 vol% YAG-Al₂O₃ nanocomposites with excellent strength characteristics at room temperature. The as-prepared powders were sintered by hot-pressing in N₂ to nearly full density with heating rate of 10°Cmin⁻¹ to 1400°C for 1h and at 30MPa pressure. The microstructure was characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscope (TEM). Microstructural results of hot-pressed composites reveal that the intergranular YAG grains of micrometer size (≈800nm) were dispersed at the grain boundaries of a dense Al₂O₃ matrix, and most fine grain YAG grains of nanometric size (≈100nm) were entrapped within the Al₂O₃ grains in the composite. The room temperature fracture strength and fracture toughness of the hot-pressed composites were 611MPa and 4.53MPa·m^−1/2, respectively. These strength and fracture toughness values are higher than those reported in other studies for YAG-Al₂O₃ system. It is proposed that the improvement of mechanical property of hot-pressed nanocomposites is due to the reduction of the grain size of the matrix and the improved strength of the grain boundaries in 25 vol% YAG-Al₂O₃ nanocomposite.