Benjamin ZIELINSKI's thesis defense

The aim of this thesis work was to study the impact of the magneto-welding process on material properties, as well as the characteristics of the resulting joint. Various pairs of materials were studied, with particular attention paid to the Copper/Copper (Cu/Cu) and Aluminium/Copper (Al/Cu) pairs.

To evaluate these joints, various characterization techniques were used and at different scales in order to assess weld quality from a global scale (macro), to a finer scale (micro). Destructive tensile and compression tests demonstrated that these tests were not sufficient to characterize the joints produced and assess their health. However, nano-indentation tests enabled us to assess in greater detail the changes in mechanical properties induced by magneto-welding, particularly at the interface. These mechanical properties were then correlated with microstructural properties using various EBSD measurements. It was possible to determine that the variations in hardness observed could be linked to local recrystallization of the interface for Cu/Cu welds.

This work also proposes an innovative approach to the non-destructive characterization of this type of joint, using X-ray micro-tomography to probe the joint interface. In particular, this method made it possible to reconstruct in 3D the contact interface, between the two dissimilar welded materials.

This method also made it possible to define two types of vortex at the interface, with different morphologies.

These different analyses provide new insights into the understanding of magneto-welding-induced evolutions, and possible explanations to improve our understanding of the formation of this type of weld.

Microstructural characterization, Magneto-welding, Micro-tomography, Mechanical testing, Interface, High-speed impact welding, Interface