Microstructure evolution and self-propagating reactions in Ni-Al nanofoils: An atomic-scale description

The relation microstructure/process in the case of self-propagating reactions in Ni-Al nanofoils was investigated by means of molecular dynamics simulations. We studied the possibility of a stationary self-sustaining reactive wave while varying the initial temperature (from 300 to 800 K) and stoichiometry (from 0.35 to 0.77 of Ni mole fraction). The main features of the wave propagation were obtained. The products of the reaction, and their microstructure along the sample after the passage of the front were described. Along with the formation of a melted alloy Ni-Al at high temperatures, the crystallized intermetallic compound B 2 -NiAl was observed. Two formation mechanisms of B 2 -NiAl were identified: dissolution-precipitation and rapid crystallization from melts. The present study proves that the microstructure differs widely according to the stoichiometry and initial temperature.