TiC nucleation/growth processes during SHS reactions

Observations of microstructure development during the formation of TiC from Ti and C are presented. Two different graphites as well as a quenching technique were used to study the effect of carbon grain size on nucleation and growth of TiC. In the case of small (7 μm) C particles, a quenched sample presents two distinct microstructures: large TiC crystals nucleated at the interface of liquid and solid Ti, and TiC nanocrystallites quenched from the melt. With Ti and C particles of the same diameter (∼ 20 μm), TiC nucleated on solid C particles. Finally, time resolved infrared thermography coupled with SEM observations is used in order to correlate temperature profiles and TiC microstructures. It is demonstrated that cooling rate and combustion temperature are the main factors controlling grain growth.