**4. Conclusions**

5A06 aluminium alloy and 321 stainless steel were welded by VFAW using an AA3003 interlayer and joints with good structure and properties were obtained. With input energies of 6 kJ, 8 kJ, and 10 kJ, the shear and tensile strengths are increased due to increased welded area. The joints with the best mechanical properties were obtained at the input energy of 10 kJ, which had a failure load of 44 kN in lap shear mode and 2.15 kN in peel mode of loading. Microstructure characterization revealed a wavy pattern between the flyer and interlayer which have similar properties. The interface between the interlayer and target showed the presence of IMCs, identified as Al3Fe and FeAl, which were continuously or intermittently distributed along the interface depending on the input energy. The results show that the use of an interlayer is a viable solution for impact welding of materials which are otherwise difficult to weld.

**Author Contributions:** Data curation, S.S.; Funding acquisition, S.C. and G.D.; Investigation, S.S. and A.V.; Methodology, A.V.; Project administration, S.C.; Software, J.X.; Supervision, G.D.; Writing—original draft, S.S.; Writing—review & editing, Y.M.

**Funding:** This research was funded by National Nature Science Foundation of China (Grant Number 51575012). The OSU work was funded by the Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technology Office under award number DE-0007813. The author gratefully acknowledges financial support from China Scholarship Council.

**Conflicts of Interest:** The authors declare no conflict of interest.

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