MICROSTRUCTURAL CHARACTERIZATION OF STRUCTURAL CERAMICS USING IMAGE-PROCESSING AND ANALYSIS

Digital imaging and analysis methods are applied to the quantitative s tudy of microstructural changes which occur during hot-pressing of ytt ria-doped silicon nitride. Effects of processing changes upon the grai n growth and microstructural anisotropy are described. Relationships b etween grain cross-sectional area and mechanical properties are establ ished. It was found that, over the range of processing conditions used , increases in grain size correlated strongly with an increase in frac ture toughness. The grain size distribution broadened significantly wi th hot-press time, resulting in reduced flexural strength. Although no significant change in the mean grain shape factor was observed, the v ariance in shape factor decreased as the hot-press time was extended.