Effect of nickel addition on the combustion reaction of the Ti–C system during mechanical alloying

Abstract

The explosive reactions or self-propagating high temperature synthesis (SHS) take place during milling Ni₂₀Ti₅₀C₃₀ and Ni₅₀Ti₃₀C₂₀ elemental powder mixtures. The coexistence of agglomerates and powders in products indicates the occurrence of melting and solidification. TiC phase and NiTi compound were obtained during millingNi₂₀Ti₅₀C₃₀, while no compound of nickel and titanium was observed when milling Ni₅₀Ti₃₀C₂₀, the final product of which is TiC and Ni. It is suggested that the explosive reaction is ignited by the heat releasing from initial formation of TiC through heavy collisions of milling balls, and the reaction between Ni and Ti, as well as the existence of Ni–Ti liquid, make the following reaction self-sustained. The variation of the addition of nickel did not affect the reaction time in both compositions, but made the reaction temperature different due to the difference of composition of Ni and Ti. It is estimated that the temperature during the reaction in Ni₂₀Ti₅₀C₃₀ rises above 1112 °C, while in Ni₅₀Ti₃₀C₂₀, it might rise above 1349 °C. However, no phenomenon suggests the melting of pure elemental Ti; the formation of TiC is mainly controlled by the diffusion mechanism in SHS.