Combustion synthesis of Ni3Al by SHS with boron additions

The preparation of Ni3Al intermetallic compound from elemental powder compacts with the addition of boron was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of the boron content, preheating temperature, and particle size of the reactants on the combustion characteristics, as well as on the composition and morphology of final products were studied. Experimental observation indicates that the addition of boron results in a significant increase in the flame-front propagation velocity, leading to a two-stage combustion process preceded by the fast propagation of the flame front and consecutively followed by prolonged bulk combustion. However, the combustion temperature was slightly decreased by adding boron in the sample. The boron addition also contributed to a decrease in the activation energy associated with the combustion synthesis of Ni3Al from 97.8 to 86.4 kJ/mol. In contrast to the presence of an intermediate phase (NiAl) and the unreacted Ni in the final burned product of the boron-free samples, complete reaction yielding a single-phase product of Ni3Al was achieved for the boron-added samples. Moreover, the addition of boron also increased the density of the final products up to above 80% relative to the density of the Ni3Al compound.