DEFORMATION-BEHAVIOR OF AN AL2O3-Y3AL5O12 EUTECTIC COMPOSITE IN COMPARISON WITH SAPPHIRE AND YAG

The relationship between a composite and its constituents with respect to high-temperature deformation behavior was investigated using the A l2O3-Y3Al5O12 (YAG) eutectic system. The eutectic is essentially a com posite with sapphire and YAG as the two phases with a volume fraction of YAG of 0.45. The deformation behavior of the eutectic and those of single-crystal sapphire and YAG were studied under identical condition s, using constant-strain-rate compression tests in air at 1530-degrees -C. The composite was also studied at 1650-degrees-C and compared with existing data on sapphire and YAG. The stronger YAG phase was found t o reinforce the sapphire matrix at higher strain rates, but the compos ite crept faster than sapphire at lower strain rates. It is suggested using a simple semiempirical analysis that diffusional relaxation at t he YAG-sapphire interface boundaries may cause the inferior creep beha vior at lower strain rates.