Texture development in silicon nitride-silicon oxynitride in situ composites via superplastic deformation

Silicon nitride-silicon oxynitride (Si3N4Si2N2O) in situ composites have be en fabricated via either the annealing or the superplastic deformation of s intered Si3N4 that has been doped with a silica-containing additive, In thi s study, quantitative texture measurements, including pole figures and X-ra y diffraction patterns, are used in conjunction with scanning electron micr oscopy and transmission electron microscopy techniques to examine the degre e of preferred orientation and texture-development mechanisms in these mate rials. The results indicate that (i) only superplastic deformation can prod uce strong textures in the beta -Si3N4 matrix, as well as Si2N2O grains tha t are formed in situ; (ii) texture development in the beta -Si3N4 matrix ma inly results from grain rotation via grain-boundary sliding; and (iii) for Si2N2O, a very strong strain-dependent texture occurs in two stages, namely , preferred nucleation and anisotropic grain growth.