FABRICATION AND MECHANICAL-PROPERTIES OF FINE-TUNGSTEN-DISPERSED ALUMINA-BASED COMPOSITES

The mechanical properties and microstructure of fine-tungsten-disperse d alumina-based composites, which were fabricated by hot pressing a mi xture of fine alpha-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 con tent and sintering condition were selected (typically 5-10 vol% W and sintered at 1400 degrees C), the fracture strength was enhanced compar ed with that of monolithic Al2O3. The metal content dependence of Youn g'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 ot her hand, high-temperature (1600 degrees C) sintering caused degradati on in the properties of the composites due to the grain growth and che mical reaction of W dispersion, which was revealed by X-ray photoelect ron spectroscopy analysis. The relations between fabrication condition and mechanical properties are discussed.