Effects of sintering condition on mechanical properties of monazite-coated alumina-fiber/alumina-matrix composites fabricated by hot-pressing

Monazite(LaPO4)-coated alumina-fiber/alumina-matrix composites were fabricated by hot-pressing, and effects of sintering temperature, sintering time, applied load and fiber volume fraction on mechanical properties of composites were examined. Better fiber debonding of coated fiber than that of non-coated fiber in the composites was observed. All composites using coated fibers showed non-catastrophic failure when hot-pressed under 40 MPa for 1 h below 1250degreesC, but failure behavior of the composite changed into completely brittle over this temperature. Higher sintering temperature, pressure and longer sintering time corresponded to higher bulk density as well as higher fracture strength, while pseudo-ductility of the composites was reduced with increasing sintering temperature. Increase of hot-pressing pressure and time did not cause a significant ductility reduction of the composites except for increase in bonding of fiber-cloths with matrix sheets. Maximum fracture strength, bulk density and pseudo-ductility of the composites obviously increased with increasing fiber volume fraction under the present hot-pressing condition.