Modeling nonisothermal interaction kinetics in the condensed state: A diagram of phase formation mechanisms for the Ni–Al system

Abstract

Nonisothermal interaction in condensed Ni–Al system takes place during combustion synthesis (CS) or the so-called self-propagating high-temperature synthesis, which is characterized by a high heating rate, high final temperature, fast accomplishment of interaction, and unconventional, nonequilibrium phase formation mechanisms. In this work, a kinetic model for phase formation during CS of nickel monoaluminide in a layered Ni–Al system is developed basing on the diffusion-controlled growth of a solid product layer in strongly nonisothermal conditions. The model includes competition between the growth of NiAl and its dissolution in the parent phases (Al-base melt and solid or liquid Ni-base solution). For numerical calculations, real values of diffusion parameters in NiAl and the Ni–Al phase diagram are used. Simulation has revealed the existence of critical heating rates that correspond to a transition from the common diffusion-controlled growth mechanism to quasiequilibrium dissolution-precipitation pattern and then to nonequilibrium crystallization route. Thereby the existence of uncommon interaction pathways during CS of intermetallics, which were observed experimentally and debated in literature, is proved theoretically ex contrario. A map of phase formation mechanisms for reaction Ni+Al→NiAl in nonisothermal conditions is constructed, which defines the applicability domains of previously known theoretical approaches and permits predicting the interaction route.

Ignition of Iron-Coated and Nickel-Coated Aluminum Particles Under Normal- and Reduced-Gravity Conditions

“…As shown in the SEM images, some layer thicknesses and grain sizes are comparable with the practical particle size range. Similarly, the heating rates in the conducted experiments were significantly lower than those in applications; the effects of heating rate on the combustion of Ni-Al system have been demonstrated experimentally [3,9] and theoretically [17]. Thus, a direct application of the obtained results to smaller particles is difficult.…”

Reactive multilayers fabricated by vapor deposition: A critical review

“…Oscillatory reactions in planar multilayers have been predicted based upon numeric and analytical models [198][199][200]. The calculations of Jayaraman et al demonstrate large variations in the temperature, the reaction zone width, the flame thermal width, and the instantaneous propagation speeds of unsteady fronts [198].…”

Interdiffusion of Ni-Al multilayers: A continuum and molecular dynamics study

“…Continuum modeling of the self-propagating reactions of Ni-Al reactive multilayered foils usually assumes that the diffusion process is Fickian, governed by an interdiffusion coefficient that only depends on temperature and is characterized by a single activation energy [12][13][14][15][16]. However, since intermetallic compounds can form during the mixing process, the reaction path could deviate significantly from this simple picture.…”

“…When a small but concentrated pulse of energy such as an electric spark or a thermal pulse is provided, highly exothermic, self-propagating chemical reactions can be triggered that proceed very quickly. The Ni-Al multilayer is often used as model system and as such it has been widely investigated systems both in experiment [1][2][3][4][5] and in continuum studies [6][7][8][9][10][11][12][13][14][15][16]. Recently, these multilayers have received increased attention because of their potential application as controllable, localized heat sources for joining microelectronic components without damage and as useful tools for forming near-net shape intermetallics [17][18][19].…”