Dynamics of intermetallics formation in the Al/Ni reactive wetting system

Abstract

Due to the complexity of interfacial reactions during reactive wetting process at high temperatures, the intrinsic mechanism behind the formation and growth of intermetallic compounds (IMCs) is still unclear. This study presents insight into the possible formation of Al/Ni IMCs in the Al (l)/Ni (s) wetting system at 1023.15 K using molecular dynamics (MD) simulation. The reactive wetting process has been broadly classified into three regimes based on the Al/Ni interphase condition: fast spreading (mostly non-reactive), crossover (dissolutive), and slow-spreading (reactive). It is found that the intermetallic phases are nucleated during the dissolutive phase; however, the stable IMCs are formed during the reactive stage and are mostly composed of AlNi and Al3Ni5. The growth of IMCs in the radial direction shows the same behavior as the contact radius of the droplet, which is a significant increase of both the droplet radius and IMCs growth in the radial direction before the droplet reaches its quasi-equilibrium base radius. Quasi-equilibrium droplet radius occurs when changes in droplet radius are negligible. In a quasi-equilibrium regime, no significant change in droplet radius and IMCs growth is observed. In contrast, the IMCs growth in the normal direction shows the opposite behavior: the thickness of IMCs increases significantly during the quasi-equilibrium regime.