Fabrication and mechanical properties of fine-tungsten-dispersed alumina-based composites

The mechanical properties and microstructure of fine-tungsten-dispersed alumina-based composites, which were fabricated by hot pressing a mixture of fine α-Al2O3 and W powders, have been investigated. Small W particles of approximately 140 nm average size were located within the Al2O3 matrix grains. The mechanical properties were influenced by the metal content and sintering conditions. When the appropriate W content and sintering condition were selected (typically 5–10 vol% W and sintered at 1400°C), the fracture strength was enhanced compared with that of monolithic Al2O3. The metal content dependence of Young's modulus and the Vickers hardness did not obey the rule of mixtures. This may be attributed to the presence of localized residual stress caused by the incorporation of fine W dispersion into Al2O3. On the other hand, high-temperature (1600°C) sintering caused degradation in the properties of the composites due to the grain growth and chemical reaction of W dispersion, which was revealed by X-ray photoelectron spectroscopy analysis. The relations between fabrication condition and mechanical properties are discussed.