On the Mechanism of Structure Formation During Combustion Synthesis of Titanium Silicides

ABSTRACT

The mechanism of structure formation during combustion synthesis of titanium silicides was investigated. It is shown that the propagation of an adiabatic combustion wave in a 5Ti + 3Si mixture follows the reaction coalescence mechanism, resulting in fine grains of Ti₅Si₃ crystallizing in the volume of melt. These grains grow rapidly behind the combustion front. Only the Ti₅Si₃ phase appears at the combustion temperature (2130°C), while other silicides (Ti₅Si₄, Ti₃Si, etc.) may crystallize in the cooling zone. Time-resolved X-ray diffraction (TRXRD) analysis of the combustion process and layer-by-layer XRD analysis of the quenched combustion wave were utilized to study the sequence of phase formation. Interaction below the melting point of Ti is negligible in the self-propagating synthesis mode. A particle-foil technique was used to investigate the details of this lower temperature interaction.

Key Words:

• Combustion synthesis
• titanium silicides
• materials synthesis
• reaction mechanisms
• structure formation.