Enhanced reactivity of Ni-Al reactive material formed by cold spraying combined with cold-pack rolling

Near-fully-dense (porosity<1%) Ni-Al reactive bulk materials were obtained by cold spraying and large deformation without crack was successfully achieved by the subsequent gradual cold-pack rolling, and the largest total thickness reduction could reach 95%. The influences of cold-pack rolling on the reactivity of the cold-sprayed Ni-Al reactive materials were investigated. The material reactivity was addressed through the solid-state reaction threshold temperature in thermal explosion mode conducted by differential scanning calorimetry and combustion wave velocity in self-propagating mode measured by a high-speed camera. For the cold-sprayed materials with rolling treatment, the onset of solid diffusion reaction shifted to a lower temperature range by 30–40 °C in the DSC experiment. An obvious increase in the combustion reaction reactivity of the cold-sprayed samples after treatment with cold-pack rolling was demonstrated. The combustion wave velocities for the materials with fifteen gradual rolling passes could reach 130–140 mm/s. The combustion reaction velocity showed a linear dependence on the statistic results of contact area per unit volume (S_v) between Ni and Al reactants and an expression was proposed, giving an activation energy of 129 kJ/mol.