SHS compactification of titanium nickelide: mechanical activation, combustion, structure, and properties

The conducted research relates to the works on obtaining consolidated materials by the method of self-propagating high-temperature synthesis (SHS) with subsequent compaction of hot products (SHS compaction). By the method of SHS compaction of mechanically activated mixtures of Ni and Ti powders, pore-free samples of titanium nickelide with a diameter of 70 mm and a thickness of 8 mm were obtained. The combustion of the Ni + Ti mixture was carried out in a reaction mold without preliminary heating and a protective environment. The effect of mechanical activation in a ball mill on the characteristics of the mixtures and the combustion parameters was studied. The analysis of the microstructural characteristics showed that an increase in the reactivity of Ni + Ti MA mixtures and the implementation of exothermic interaction in the SHS mode are due to a decrease in the crystallite size in Ni particles, an increase in the dislocation density in them and the formation of composite Ti–Ni particles. The maximum combustion temperature of the reaction mixture is 1150$^{\circ}$C, the average combustion velocity is 3.5 cm/s. The main phases of the synthesized alloy are Ti$_2$Ni, NiTi and Ni$_3$Ti. The compressive strength of the samples is 1350 MPa, the Vickers microhardness is 11.1 $\pm$ 1.2 GPa.