PLASTIC-DEFORMATION MECHANISMS IN SIC-WHISKER-REINFORCED ALUMINA

SiC-whisker-reinforced Al2O3 samples (SiC(w)/Al2O3), obtained from thr ee different manufacturers, containing 0-30 vol% SiC have been crept u nder compression at 1400-degrees-C in flowing argon. Compressive creep tests and microstructural observations have been used to characterize the plastic deformation mechanisms. The presence of whiskers decrease d the creep rate by reducing grain-boundary sliding. Damage formation was increased, however, because the whiskers acted as stress concentra tion sites. For specimens with whisker loadings greater than 15%, the absolute creep rate was not strongly dependent on whisker concentratio n, and the formation of cavitation damage was negligible below a criti cal stress that depended on the fabrication procedure of the specimen. This creep regime was characterized by a stress exponent of approxima tely 1, in which deformation occurred primarily by diffusional flow. F or the materials with less SiC, the deformation occurred primarily by grain-boundary sliding.