R-curve behaviour and microstructure of liquid-phase sintered α-SiC

R-curves for two liquid-phase sintered alpha-SiC (SC-A and SC-B), of different microstructures, were characterized using indentation-strength method. Silicon carbide SC-B, with its coarser microstructure and 8 MPa . m(1/2) toughness, showed higher resistance to crack growth and more damage tolerance than silicon carbide SC-A, with its finer microstructure and 4.5 MPa . m(1/2) toughness. These results suggest that a coarse microstructure is beneficial to toughening and damage tolerance while a fine microstructure is beneficial to strengthening. (C) 2000 Kluwer Academic Publishers.