Experimental and molecular dynamics simulation of wetting and spreading of Al-Si brazing filler metal on Fe Substrate: Element diffusion and interfacial compounds

In a high vacuum environment, the wetting and spreading characteristics of Al-Si eutectic brazing filler metal on the surface of pure Fe substrate were tested respectively when the maximum holding temperature was 970 K, 1000 K, and 1030 K. The Fe element in the substrate diffuses into the Al-Si brazing alloy. The Si element in the brazing alloy also diffuses into the substrate, while the Al element does not deeply diffuse into the substrate. The wetting and spreading process was calculated by using the method of molecular dynamics simulation. In order to match the Al-Si/Fe system, an improved modified embedded atom method (MEAM) potential was proposed. Utilizing the improved MEAM potential, the influence of different crystal grain orientations of Fe substrate and the presence of Si element on the wetting mechanism of aluminum-based brazing filler metal were elucidated, emphasizing elements diffusion and reaction during wetting. Simulation results indicate that pure Al and Al-12.2Si show similar wetting processes, achieving the minimum wetting contact angle on the Fe (111) crystal plane. The movement process of the molten droplet atoms can be divided into three stages: rapid contact, slow diffusion, and gradual stabilization, and this phenomenon matches the experimental results.