MORPHOLOGICAL CHARACTERIZATION OF HOT-PRESSED ALPHA-SIC WITH AL-BASEDADDITIVES DEFORMED BY COMPRESSION AT HIGH-TEMPERATURE

An automatic image analysis method has been used to study the microstr ucture evolution of polycrystalline alpha-SiC samples hot pressed with 0.3 wt% and 1.5 wt% Al-based additives after compression at high temp erature. Microstructures have been characterized in terms of grain sha pe, grain size and grain orientation with respect to the macroscopic s tress direction. If has been shown that grains tend to flatten per pen dicularly to the external stress for the 0.3 wt% Al grade. By contrast , for the same macroscopic deformation value, grains of the 1.5 wt% Al grade do not exhibit any shape change after creep tests, suggesting t hat a certain amount of super plastic deformation has occurred.