Effect of titanium content and mechanical activation on $\mathrm{Ni}$–$\mathrm{Al}$–$\mathrm{Ti}$ combustion

This paper describes the effect of preliminary mechanical activation (MA) and $\mathrm{Ti}$ content on a maximum temperature, a maximum burning rate, the size of composite particles, the yield of a mixture after MA, the elongation of samples during combustion, and the phase composition and morphology of combustion products in the $\mathrm{Ni}$–$\mathrm{Ti}$–$\mathrm{Al}$ system. The preliminary MA of a $\mathrm{Ni}+\mathrm{Al}+\mathrm{Ti}$ mixture expands the limit of titanium content at which samples can burn without preheating, from 17 to 59% (by weight). Mechanical activation reduces the number of phases in the products and increases the burning rate, while the maximum synthesis temperature decreases. An increase in the $\mathrm{Ti}$ content in the $\mathrm{Ni}+\mathrm{Al}+\mathrm{Ti}$ mixture reduces the rate and maximum combustion temperature of both the initial and MA mixture. In addition, as the titanium content increases, the average size of composite particles decreases and the yield of the activated mixture becomes larger. During the combustion of MA mixtures with a high (24–52%) titanium content, the $\mathrm{Ti}_2\mathrm{Ni}$ phase and the $\mathrm{Ni}_2\mathrm{TiAl}$ Heusler phase predominate in the products, and traces of melting are visually observed. In the activated $\mathrm{Ni}+\mathrm{Al}+\mathrm{Ti}$ mixture, the $\mathrm{Ti}$ content at which the content of the Heusler phase in the combustion products is maximum is revealed. For most of the observed dependences, an explanation is proposed.