Alloying propagation in nanometric Ni/Al multilayers: A molecular dynamics study

Abstract

In nanometric metallic multilayers such as Ni/Al, the alloying reaction proceeds in the form of a propagating wave. We studied the different phase transformations involved in the reactive wave propagation by means of molecular dynamics. The focus was on a specific regime that involves melting of reactants, intermixing of reactants and formation of an intermetallic compound. We found that the wave consists in two stages. The first front is associated with a dissolution process and propagates at several meters per second while the second front is due to the crystallization of the final product and is slower leading to a specific microstructure with alternated large grains of NiAl and liquid regions in the front propagation direction. Three main exothermic processes were identified, including grain coarsening. Their respective contributions were evaluated. We developed a new texture analysis tool that allowed us to follow the evolution of the microstructure and the dynamics of the grain orientation.

SHS in Ni/Al Nanofoils: A Review of Experiments and Molecular Dynamics Simulations

“…The rotation matrix which embodies the rotation of the sample coordinates onto the crystal (grain) coordinates is then computed. The method allowed us to get the Euler angles and the Miller indices of a collection of grains with respect to the sample …”

“…In fact, it is a serious advantage in order to investigate the reactive wave propagation in the framework of MD simulations. To do so, the length of the sample in the direction of the reactive front propagation has to be larger than that in the conduction zone (see e.g.,). In experiments, the thickness of the conduction zone is around 2–10 µm .…”

“…The initial conditions play a important role both in the evolution of the microstructure and SHS features as shown in ref. . In most situations, the propagation is driven by exothermic dissolution and intermixing.…”

Self-Powered Fast Brazing of Ti-6Al-4V Using Ni/Al Reactive Multilayer Films

“…In the context of the RMF reaction, first the Al layers melt, then, the solid Ni layers dissolve in the molten Al and this is concluded by crystallization of Ni-Al intermetallic compounds. Melting and dissolution occurs during reaction propagation and crystallization occurs after the end of the propagation phase [17,18]. Al (111) Ni (200) AlNi (111) AlNi ( the RMF.…”

Effect of the Particle Size of Al/Ni Multilayer Powder on the Exothermic Characterization

“…The extraordinary features of the exothermic reaction of Al and Ni are beneficial for a wide range of practical applications such as the solder joining of silicon devices [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ] and the initiation of neighboring injections [ 17 , 18 , 19 ]. For a smooth exothermic reaction, a stacked nanoscale-thick bilayer structure fabricated by a thin-film technology such as sputtering or plating techniques is required [ 20 , 21 , 22 , 23 ]. The sputtering method is a conventional and widely used technique for fabricating a nanoscale-thick bilayer structure because the exothermic heat can be adjusted by controlling the atomic concentration of Al and Ni atoms.…”