TOUGHENING OF X-SIALON WITH AL2O3 PLATELETS

Toughening of an X-sialon matrix with up to 53 volume percent Al2O3 pl atelets was investigated. The effect of platelet content on both matri x phase composition and mechanical properties of the composites was ev aluated. The extent of cracks introduced by Vickers hardness indentati ons showed a reduced length with increasing platelet content, indicati ng an increase in fracture toughness. The toughness has been shown to increase from 1.77 MPa . m(1/2) for pure X-sialon up to 4.16 MPa . m(1 /2) for the composite containing 28 volume percent platelets. For high er platelet additions, toughness increases further but the composition of the matrix shifts to beta'-sialon. The E-modulus of the composites increases with the amount of platelets. The improvement in fracture t oughness was attributed to debonding, crack bridging and crack deflect ion.