The effect of an electric field on the microstructural development during combustion synthesis of TiNi–TiC composites

Abstract

The role of an externally imposed (contacting) electric field on the microstructural development during the synthesis of TiC–TiNi composites was investigated. Using elemental reactants, composites with 60 and 70 vol% TiNi were synthesized by the self-propagating combustion method. The field had a direct effect on the velocity and temperature of the combustion wave, and had an influence on the particle size of the TiC phase formed within the TiNi matrix. The average particle size increased by at least a factor of two (from about 2.5 to 5.5 μm for the 60 vol% TiNi samples and from 1.5 to 3.0 μm for the 70 vol% TiNi samples) as the field strength was increased from zero to about 5 V cm −1. Although higher temperatures and wave velocities result in higher temperature gradients and thus an anticipation of shorter residence time at the highest temperatures, the presence of a liquid phase has apparently a more direct effect on TiC particle growth. In cases where no liquid is present the results are different, as will be reported in a subsequent paper.