On the Disintegration of A1050/Ni201 Explosively Welded Clads Induced by Long-Term Annealing

The paper presents the microstructure and phase composition of the interface zone formed in the explosive welding process between technically pure aluminum and nickel. Low and high detonation velocities of 2000 and 2800 m/s were applied to expose the differences of the welded zone directly after the joining as well as subsequent long-term annealing. The large amount of the melted areas was observed composed of a variety of Al-Ni type intermetallics; however, the morphology varied from nearly flat to wavy with increasing detonation velocity. The applied heat treatment at 500 °C has resulted in the formation of Al₃Ni and Al₃Ni₂ layers, which in the first stages of growth preserved the initial interface morphology. Due to the large differences in Al and Ni diffusivities, the porosity formation occurred for both types of clads. Faster consumption of Al₃Ni phase at the expense of the growing Al₃Ni₂ phase, characterized by strong crystallographic texture, has been observed only for the weld obtained at low detonation velocity. As a result of the extended annealing time, the disintegration of the bond occurred due to crack propagation located at the A1050/Al₃Ni₂ interface.