SILICON-CARBIDE FIBER-REINFORCED ALUMINA EXTRUSION

Silicon carbide fiber-reinforced alumina bodies have been produced by ram extrusion. The Al2O3 powder and SiC fiber were milled together to give a dry dispersion of up to 30 vol% fiber which was subsequently mi xed to a paste by high shear kneading using hydroxypropylmethylcellulo se solutions as the binder phase. Extruded bodies with green densities ranging between 56 and 63% full theoretical density were achieved. Th e paste flow behavior was characterized using physically based equatio ns which show that for any given moisture content the pressure drop an d the constituent paste parameters are all systematically reduced as t he fiber loading is increased. This observation can be explained almos t completely by combining packing theory with the paste theology data. Fiber interactions within the paste and the die system appear not to greatly influence the theological character of the material. It is sho wn statistically that the fibers are homogeneously dispersed throughou t the paste mass after extrusion. Image analysis has been used to aid in macrodefect analysis, and it is shown that the optimum concentratio n of fiber was 20 vol% with a quantity of binder sufficient to give an initial yield stress of 2 MPa.