ACOUSTIC STUDIES OF THE EFFECT OF SIC PARTICLE REINFORCEMENT ON THE COMPACTION OF ALUMINA POWDER

A number of acoustic techniques namely, ultrasonic (US), acousto-ultra sonic (AU) and acoustic emission (AE), were employed to study the effe ct of reinforcement in the form of SiC particles on the compaction of spray-dried alumina powder. The US and AU techniques were shown to be capable of monitoring the processes occurring during loading and unloa ding, whereas AE could be used, in certain cases, to monitor the relat ive movement of particles in a powder compact during stress relaxation . The results were consistent with three stages of compaction, namely rearrangement of agglomerates, agglomerate breakdown and elastic defor mation. The two pressure break-points between the stages, i.e. P-1 and P-2 the pressures corresponding to the onset of breakdown of the aggl omerates and to the change from permanent to elastic deformation, resp ectively, were determined by a number of different methods as a functi on of SiC content (10-40 vol%), type (equiaxed, angular or platelet) a nd size. (C) 1997. Published by Elsevier Science Limited.