Mechanical properties of alumina-rich magnesium aluminate spinel/tungsten composites

The mechanical properties and microstructure of alumina-rich magnesium aluminate spinel/tungsten (14 and 22 vol.% W) composites obtained by hot press at 1650 °C under reducing conditions have been investigated. The R-curve for these composites was estimated by the indentation strength method and compared with that of the monolithic spinel obtained under similar conditions. Rising R-curve behavior was specially observed in the composites when tungsten content was higher. Other mechanical properties such as hardness, toughness, Young's modulus and bending strength, were also determined for both (composites and monolithic magnesium aluminate). Higher values of bending strength were found as the metal volume fraction increases in the composite. The metal content dependence of Young's modulus and Vickers hardness follow the rule of mixtures. Mechanical properties and specially toughness are influenced by the metal content and its grain size.