Diffusion welding of aluminium alloy strengthened by Al2O3 particles through an Al/Cu multilayer foil

[Display omitted] ► We studied deformational behaviour of multilayer foil at heating under load. ► It is shown that such foils undergo superplastic flow at certain temperatures. ► Comparison of conditions welding through foil and its plastic flow was performed. ► Temperatures of welding and superplasticity of foils correlate with each other. ► A mechanism of welded joint formation through multilayer foil is proposed. In the diffusion welding (DW) of difficult-to-deform materials (such as composites and intermetallics), the application of intermediate multilayer foils (MF), which have alternating layers of elements that form intermetallics, allows for production of a permanent joint under milder conditions. In this paper, the processes occurring in the joint zone (JZ) during DW of Al–5wt.%Mg+27wt.%Al2O3 composite material through the Al/Cu interlayer were studied. It was shown that, while heating of such a foil, phase transformations that are due to the reaction diffusion of elements, run in it. At MF heating under a continuously applied external load, the materials are plastically deformed. It is established that the intensity of foil plastic deformation at a specified load non-monotonically depends on temperature. It is shown that welding temperature is determined by the temperature at which MF can undergo superplastic flow under the impact of applied pressure. A mechanism of formation for a solid-phase joint of high-strength materials through interlayers based on the MF of intermetallic-forming elements is proposed.