Ultrasonic erosion of whisker-reinforced ceramic composites

Uniaxial hot-pressing of SiC whisker reinforced Al2O3 ceramic composites in duces an anisotropy in whisker distribution and leads to a composite with a nisotropic mechanical properties. In this paper, the effects of whisker ori entation on the material removal rates arid mechanisms in ultrasonic machin ing of Al2O3/SiCw ceramic composites are reported. It was found that the ma terial removal rates and machined surface roughness in ultrasonic machining of the composites varied according to the angle theta to the hot pressing direction. The maximum material removal rate and surface roughness were obs erved for the machining surface perpendicular to the hot-pressing direction (theta =0 degrees), and the minimum ones were observed for the machining s urface parallel to the hot-pressing direction (theta =90 degrees). This eff ect was larger for specimens with higher SiC whisker content. Based on the lateral crack fracture analysis in ultrasonic machining of the composites, the mechanisms responsible for the anisotropy in material removal rates cau sed by whisker orientation were investigated. (C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.