Effect of MoSi2 and Nb reinforcements on mechanical properties of Al2O3 matrix composites

The room temperature mechanical properties of Al2O3 composites reinforced w ith 25 vol% of either MoSi2 or Nb particulates were investigated. It was fo und that addition of Nb particles resulted in a reduction in the elastic mo dulus, but caused a significant increase in both flexural strength and frac ture toughness. On the other hand, the addition of MoSi2 particles resulted in only a marginal decrease in elastic modulus and marginal increase in bo th flexural strength and fracture toughness. The elastic modulus results we re explained on the basis of Tsai - Halpin model. For both the composites, the increase in flexural strength was attributed to the grain refinement of the Al2O3 matrix as well as the load transfer to the reinforcement particl es. The marginal increase in fracture toughness in Al2O3 / MoSi2 composites was attributed to crack deflection, whereas the threefold increase in frac ture toughness in Al2O3 / Nb composites was attributed to crack blunting an d bridging. (C) 2000 Kluwer Academic Publishers.