Reaction mechanism of self-propagating high-temperature synthesis reaction in the Ni-Ti-B4C system

The SHS reaction in the Ni-Ti-B4C system starts with the formation of Ni-Ti and Ni-B intermetallic compounds from the solid interacted reaction among the reactants and, subsequently, the formation of Ni-Ti and Ni-B liquid at the eutectic point. Meanwhile, some C atoms from the reaction between Ni and B4C can dissolve into Ni-Ti liquid to form TiC. The heat generated from these reactions can promote the mutual diffusion of Ni-Ti-C and Ni-B liquid and simultaneously accelerate the formation of Ni-Ti-C-B liquid. Finally the precipitation of TiC and TiB2 occur when the C and B atoms in the liquid become supersaturated. The addition of Ni not only promotes the occurrence of the self-propagating high temperature synthesis (SHS) reaction by forming Ni-Ti liquid, but also accelerates the SHS reaction by forming Ni-B liquid and dissociative C. The early appearance of dissociative C from the reaction between Ni and B4C causes the formation of TiC prior to that of TiB2.