Characterization of local mechanical properties of Al/Cu Magnetic Pulse Welded joints under high strain rates using synchrotron X-ray imaging

Abstract

Magnetic Pulse Welding (MPW) is a method of growing interest allowing the joining of dissimilar materials such as aluminum and copper. The global mechanical properties of the joint are often evaluated with conventional tests, using the fully welded joint. However, these cannot elucidate the local mechanical properties of the joint or its interface when subjected to high strain rates loads. Cubic samples of Al/Cu have been designed and extracted from MPW joints, in order to locally characterize the mechanical properties. Samples were exposed to high strain-rate loading using the Split-Hopkinson Pressure Bar (SHPB) coupled to ultra-fast synchrotron X-ray radiography in order to investigate related failure processes in-situ. The measurements of the interface evolution were related to the macroscopic applied load. In addition, synchrotron microtomography was performed on the samples before mechanical deformation. Aside from the feasibility proof, this work provides, for the first time, the correlation of the interfacial opening evolution and the influence of pre-existing cracks of the weld. It is observed that, the pre-existing cracks at the interface correspond to the initiation sites of interfacial separation between the two dissimilar metals.