Evaluation of the macro/microstructure of Al/Cu/Sn/Ni multi-layered composite produced by accumulative-roll-bonding (ARB) and post-heat treatment

In this study, an Al/Cu/Sn/Ni multi-layer composite (MLC) was produced by a two-step process (i.e., accumulative roll bonding and subsequent heat treatment) for up to six cycles. The effect of the two-step process on the macro/microstructure of the Al/Cu/Sn/Ni MLC was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, and x-ray diffraction pattern. The results show that the Ni and Sn layers in the sandwich cycle and the Cu layer in the 1st cycle fractured in the Al matrix. Finally, during the 6th cycle of the two-step process, a uniform distribution of Ni, Cu, and Sn reinforcement layers was achieved in the Al matrix. Moreover, during the 3rd cycle, an Al3Ni2 intermetallic compound was formed at the interface of the Al/Ni layer. Also, during the 6th cycle, in addition to the formation of the Al3Ni2, an AlCu intermetallic compound was formed at the interface of the Al/Cu layer. The recrystallization phenomenon in the Al matrix occurred during the sandwich, 3rd, and 6th cycles, too. In addition, during the various cycles, grain growth also occurred in the Al matrix so that the size of some grains in the Al matrix during the 3rd and 6th cycles reached about 2 and 1 µm, respectively. •Filling of cracks at the interface of the layers by the molten Sn layer.•Formation of AlCu and Al3Ni2 intermetallic compounds during various cycles of the two-step process.•Many recrystallized grains were formed in the Al matrix during various cycles of the two-step process.•Normal grain growth has been occurred in some regions of the Al matrix during various cycles of the two-step process.