STRENGTHENING MECHANISM IN AL2O3 SIC PART ICULATE COMPOSITES/

Effects of sub-grain-boundaries (SGB) formed in Al2O3 grains and resid ual stress caused by additions of SiC particles in Al2O3 phase on the strength of Al2O3/SiC composites were investigated, The number of the SGB and the residual tensile stress in Al2O3 were found to increase wi th increasing SiC content. The experimental. results suggest that the strengthening in Al2O3/SiC composites is attributable not only to the formation of the SGB but also to the toughness increases which is poss ibly related with the residual stress. The strengthening by annealing in Ar was also investigated. The annealing resulted in the strength in crease of more than 200 MPa, whereas the annealed and subsequently gro und specimens did not show the strength increase. It is therefore conc luded that the strengthening due to the anneal is mainly caused by hea ling of surface defects.