Combustion characteristics of the Ni3Ti-TiB2 intermetallic matrix composites

Combustion synthesis (SHS) of Ni₃Ti-TiB₂ metal matrix composites (MMCs) was selected to investigate the effect of gravity in a reaction system that produced a light, solid ceramic particle (TiB₂) synthesized in situ in a large volume (>50 pct) of the liquid metallic matrix (Ni₃Ti). The effects of composition, green density of pellets, and nickel particle size on the combustion characteristics are presented. Combustion reaction temperature, wave velocity, and combustion behavior changed drastically with change in reaction parameters. Two types of density effects were observed when different nickel particle sizes were used. The structures of the combustion zones were characterized using temperature profile analysis. The combustion zone can be divided into preflame, reaction, and after-burning zones. The combustion mechanism was studied by quenching the combustion front. It was found that the combustion reactions proceeded in the following sequence: formation of liquid Ni-Ti eutectic at 940 °C → Ni₃Ti+NiTi phases → reduction of NiTi with B→TiB₂+Ni₃Ti.