Hardness and Microstructure of SiC-B₄C Eutectic Ceramics Prepared by Arc Melting

Abstract

Quasi binary SiC-B₄C and ternary Si-B-C system composites were prepared by arc melting in argon atmosphere. The Vickers microhardness (100g load) of the quasi binary SiC-B₄C composites decreased from 39 to 34 GPa with increasing SiC molar content (m_SiC) from 25 to 65 mol%. The hardness values at m_SiC=45 to 55 mol%, which is nearly the eutectic composition, was higher than those calculated from a linear law. This could be caused by fine lamella microstructures. Free C and free Si co-precipitated at the C-rich and Si-rich side of the quasi binary composition, respectively. The hardness values at the quasi binary compositions were greater than those of the C-rich and Si-rich compositions.