ALUMINA OF HIGH-RELIABILITY BY CENTRIFUGAL CASTING

Centrifugal casting is a powerful colloidal processing route for massi ve ceramic parts of high strength and high reliability. Aqueous alpha- alumina slurries with up to 56.8 vol.% solids content with a mean part icle size of 0.46 mu m were deagglomerated by ultrasonic treatment and subsequent filtration. Consolidation was performed at various centrif ugal accelerations. Differential sedimentation during centrifugal cast ing was studied and found to be negligible for slurries with high soli ds loadings exceeding 50 vol.%. Green bodies with very good particle p acking, showing high green densities of 68%TD (theoretical density), a s well as narrow pore size distributions were obtained. High sintered densities (greater than or equal to 99.4%TD) with homogeneous and fine microstructures were achieved at sintering temperatures as low as 140 0 degrees C. Four-point-bending tests showed an average strength of 54 0 MPa with a Weibull modulus m of 24.