Structure and properties of ultrafine-grained MOSi2+Si3N4 composites synthesized by mechanical alloying

Monolithic MoSi2 and MoSi2 + Si3N4 ultrafine-grained composites with 2.5 or 5.0 wt.% Si3N4 were synthesized by mechanical alloying. The microstructure and crystal structure of the phases present in the as-milled powders were determined by electron microscopy and X-ray diffraction methods. The mechanically alloyed powders were successfully consolidated to full density by vacuum hot pressing. A detailed microstructural investigation and mechanical properties (hardness and fracture toughness) evaluation of the consolidated products was presented. After consolidation, the microstructure continued to be fine-grained (in the submicron range), but no appreciable increase in the room temperature fracture toughness Of MoSi2 was observed for the composites by the addition of Si3N4. (c) 2007 Published by Elsevier B.V.