Creep of SiC-Whisker reinforced Si3N4

Abstract

The mechanical behaviour of a composite of Si3N4 (with 3 % MgO) containing 0-20 % SiC whiskers has been investigated by compressive creep experiments (100-300 MPa) at temperatures between 1 250 °C and 1 500 °C. No significant influence of the SiC whiskers on the creep behaviour could be detected up to about 5 % of strain. Two temperature regions could be identified : a) at high temperature the creep deformation occurs at a quasiconstant strain rate. Extended cavitation in the triple junctions occurs. b) At low temperatures, creep rates rapidly decrease due to a strain hardening coefficient much more important than for higher temperatures. In the microstructure, cavities and microcracks along grain boundaries and fiber-matrix interfaces were observed. Dislocations play an insignificant role for the deformation in both temperatures regions