High Temperature Strength of SiC-AlN Solid Solutions and Composites as Evaluated by Small Punch Tests

Fully dense compacts of SiC-AIN solid solution and composite were fa bricated by the combination of reaction synthesis and hot isostatic pressing(HIP)．Their strength and deformation behavior were investigated from room temperature to 1773 K by a Modified Small Punch(MSP)test which has been found to be suitable for the mechanical evaluation of brittle materials．The SiC-AIN solid solution and composite samples showed higher strength than both of the HIPed SiC (with O．5 mass％B4C additives)and AIN compacts from room temperature to 1473 K． A decrease in the strength was then observed above 1473 K for the solid solutions containing 5，10 and 25 mol％AIN， while the SiC， AIN and SiC-AIN composites maintained the room temperature strength up to 1773 K． Nonlinear deformation occurred at 1773 K in the solid solution samples with the composition of SiC-25 mol％AIN， being accompanied by a drastic drop in strength． Considering the fact that single-phase SiC-AIN solid solutions have afine microstructure of uniform grain size， the nonlinear deformation is due to grain boundary sliding． On