Reactivity in nickel–aluminum system was examined for two variants of nickel substrates in terms of the size and shape of Ni grains. The microstructure transformation aroused due to the annealing at 720 °C for different annealing times (0.25 to 72 h) was consequently followed. The sequence of formation of the particular intermetallic phases was given. The interconnection zones were examined by means of scanning electron microscopy supported with energy dispersive X-ray spectroscopy and electron backscattered diffraction techniques as well as by the transmission electron microscopy. The growth kinetics data for AlNi, AlNi_Ni-rich and AlNi₃ phases for both variants of substrates was given, indicating the differences obtained in previous works on this subject.

Explosive welding is a joining method suitable for materials difficult or impossible to connect using traditional welding techniques. In this work, the microstructure details occurring in the neighborhood of the aluminum (A1050) and nickel (Ni201) alloys’ interfaces in explosive welds were described. It was shown that using appropriate welding conditions, although the mutual localization of the colliding plates was different, the microstructure of the bonded zone did not change. Moreover, further annealing of the samples at 500 °C revealed the microstructure transformation occurring as a result of the diffusion phenomena. This in turn provides the details essential in proper designing of the multilayers of metallic–intermetallic Al/Ni composites.

The investigation is dedicated to the detailed microstructure characterization of explosively welded clads, in which, exceptionally and for cognitive purposes, a very high detonation speed of about 2800 m/s was used to manufacture bimetallic aluminum-nickel plates. The study involves detailed microstructural characteristics of the bonded zone at micro and nano level, especially focused on the expanded melted regions consisted mostly of Al₃Ni, Al₃Ni₂ and AlNi phases. In situ heating experiment in transmission electron microscope allowed observing microstructure transformation revealing that additionally present metastable Al₉Ni₂ phase was transformed to Al₃Ni and Al₃Ni₂. Microhardness measurements across the welded zone showed the increase of the microhardness of nickel alloy plate from 153 up to 170 HV when approaching to the Ni201/A1050 interface, while the value for aluminum plate was of 45 HV. Within the melted zones the microhardness was found to be 135 HV and it enormously increased to 850 HV after annealing of the sample at 500 °C. This change was due to the transformation of the interface region from the waves with the melted zones into the continuous layers of two intermetallic phases: Al₃Ni and Al₃Ni₂. The second phase grew at the expense of the Al₃Ni.

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.