The formation mechanism of dissimilar material interface using explosive welding（EW）has always been discussed among the researchers. One suggested that EW is purely a solid state welding technique, and another considered that EW is similar to fusion welding. In this study, cladding of a group V or VI refractory metal（RM）plate on a Cu plate was conducted using EW, to investigate the interface morphology and microstructure for discussion of the formation mechanism of RM/Cu wavy interfaces, which are regarded as a strong EW interface. Since, the RMs are inherently brittle in nature, a gelatin medium or an underwater medium was employed to obtain the RM/Cu clads instead of the conventional EW setup. The RM/Cu EW clads exhibited a wavy interface with various amplitude and wavelength depending on RM physical properties, except the W/Cu clad whose W plate had cracks initiating at the surface and reaching to the interface. TEM observation indicated that RM and Cu areas separated clearly at the interface without any mixing area or oxide layer. At the crest of wave in the Mo/Cu clad, metal jets were trapped due to relatively low collision angle, resulting in two phase structure consisting of ultrafine Mo and Cu grains. Many dislocations were observed in the RM grains near the interface, suggesting severe deformation, while some dislocations were observed in the recrystallized Cu grains not only below but also away from the interface. The observation indicates that dynamic deformation due to hydro pressure caused by collision of both metal plates at the collision point played a key role in formation of the interface morphology and microstructure.

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