Formation of intermetallic structures at the interface of steel-to-aluminium explosive welds

Highlights: • The interface of Fe-Al explosive welds was characterised by SEM/EDS and EBSD. • The intermetallics formed at the weld interface are rich in Al (Fe₄Al₁₃, Fe₂Al₅). • The presence of intermetallic phases on the interface deeply affects the weldability. • Al-rich intermetallics increase the solidification time of the weld interface. - Abstract: The formation of intermetallic structures at the interface of carbon steel to 6082 aluminium alloy explosive welds and their influence on the weldability of these two materials were studied. The morphology, the microstructure, the chemical and phase compositions of the welds were characterised by several types of microscopy techniques. The interface characterisation proved that explosive mixtures with a lower detonation velocity were revealed as being more suitable for achieving consistent welds since jet entrapment was prevented and continuous molten layers were not formed at the weld interface. It was also found that the physical properties of the intermetallic phases generated at the weld interface have a strong influence on the weldability of steel-to-aluminium explosive welds. Specifically, it was shown that the formation of aluminium-rich intermetallic phases at the weld interface increases the solidification time of the interfacial molten material, decreasing the weldability of these two materials. The formation of these intermetallic compounds should be avoided by reducing the interaction between the flyer and the baseplate as well as by avoiding excessive molten layers.