Microstructural evolution of SiC powder in molten silicon

SiCpowder/Simatrix composites represent a new class of microstructurally toughened materials. The interactions between molten silicon and submicronic SiC powder have been considered since it could originate some limitations on the final properties of the material. Experiments putting in interaction a SiC powder and molten Si were performed while heating up to final values ranging between 1450 and 1600 °C for duration up to 8 h. The volume ratio of SiC and silicon was equal to one and SiC particles were freely dispersed within the liquid. X-ray diffraction analyses demonstrated that the apparent crystallites size increase of SiC powder followed a ripening law corresponding to a limitation either by volume diffusion or by dissolution into the liquid. Depending on the relevant mechanism, the activation energy of the crystallites' growth has been found equal to 357 ± 50 kJ mol−1 or 441 ± 57 kJ mol−1. An agglomeration-coarsening process of SiC particles was also identified which promoted a quick formation of larger particles.