Microstructural investigations of HIP'ed silicon nitride reinforced with silicon carbide whiskers were performed using a 400 kV high resolution analytical transmission electron microscope. Two different whisker sources as well as uncoated and carbon coated whiskers were evaluated for their effectiveness in improving mechanical properties.
This paper focuses on microstructural and microchemical analysis of interface and grain boundary regions within the composites. Combined HREM and AEM investigations reveal that variations in fracture toughness are mainly influenced by the microstructural and chemical development of the interface. Fracture toughness can be related to the surface chemistry of the reinforcements.