Mechanical properties and recrystallization of alumina ceramics reinforced by silicon carbide whisker

Abstract

The mechanical properties and recrystallization of a material consisting of Al2O3 and SiC whisker are considered for different hot pressing regimes. The best properties are obtained at an SiC whisker content of 20% in hot pressing in an argon medium at 1600°C (the ultimate bending strength is 600 MPa, the critical coefficient of stress intensityKIc=5.5 MPa · m1/2). The bending strength measured at 1000°C is at least 400 MPa for the material pressed at 1700°C in air. It is established that the presence of SiC whisker on grain boundaries of Al2O3 noticeably impedes the growth of alumina grains in recrystallization for all chosen regimes of hot pressing (1650 – 1900°C, 15 – 45 min). The dominant grain size is 1 –5 µm. A mathematical model is suggested for evaluating the maximum grain size in uniform grain growth, which isD*=0.571 [1++(1+16.151/f)1/2]d, whered, f are the diameter and the volume fraction of SiC whisker. The material can be recommended for use under conditions of thermomechanical stress and abrasive wear.