Recrystallization and Phase Transformation in Reaction‐Sintered Sic

Reaction‐sintered Sic specimens prepared at ∼1500°C and heat‐treated at ∼1850°C in the presence of molten silicon were examined by transmission electron microscopy. The β‐Sic grains in as‐prepared specimens grew to a large size when heat‐treated in the presence of molten Si; the number of growth twins in such °‐Sic crystals was very small. The boundary areas of α‐ and β‐Sic crystals were microsyntactic, consisting of thin strips of α‐ and β‐Sic after heat‐treating. These changes were due mostly to thin lamellar growth of α‐Sic into β‐Sic grains along the basal plane. There is also a high density of similar growth of transformation twins in β‐Sic crystals. The results provide clear evidence of in situ solid‐state transformations in sic.