Microstructure and fracture toughness of liquid-phase-sintered β-SiC containing β-SiC whiskers as seeds

Abstract

The effect of seeding on microstructural development and fracture toughness of β-SiC with an oxynitride glass was investigated by the use of morphologically rodlike β-SiC whiskers. A self reinforced microstructure consisting of rodlike β-SiC grains and equiaxed β-SiC matrix grains was obtained by seeding 1–10 wt% SiC whiskers, owing to the epitaxial growth of β-SiC from the seed whiskers. Further addition of seeds (20 wt%) or further annealing at higher temperatures led to a unimodal microstructure, owing to the impingement of growing seed grains. By seeding β-SiC whiskers, fracture toughness of fine-grained materials was improved from 2.8 to 3.9–6.7 MPa · m1/2, depending on the seed content.