Understanding interface evolution during explosive welding of silver foil and Q235 substrate through experimental observation coupled with simulation

In this work, explosive welding was introduced to manufacture Ag coating on Fe substrate. The microstructure evolutions of the Ag/Fe joint interface and the associated governing mechanisms during the collision process, were investigated by a comprehensive study combined advanced characterizations and smoothed particles hydrodynamics simulations. It was concluded that the self-developed explosive welding process enabled to attain high-quality Ag coatings effectively, certified by absence of geometric defects at the Ag/Fe interface and the surface of Ag foil. The simulation accurately reproduced the wavy interface and vortex structure observed in experiment. From this, the evolution of the wave was reconstructed and the formation mechanism of the vortex was revealed. The microstructure analyses revealed a remarkable diversity of the grain structure near the Ag/Fe interface. The equiaxed fine grains related to dynamic recrystallization were formed in the vicinity of the interface and also within the vortex. The grains of the Fe matrix slightly away from the interface became elongated, which reflected well the deformation features. Meanwhile, the columnar grains induced by molten and re-solidified processes were observed at the vortex boundary. The variation of these grain structures was responsible for the inhomogeneity of nanoindentation hardness distribution.