Influence of Copper Interlayers on the Magnetic Pulse Welding Process between Aluminum and Steel

Joerg Bellmann,Daisy Nestler,Eckhard Beyer,Martina Zimmermann,Kristina Roder,Lothar Kroll

doi:10.3390/met11060868

Abstract

Magnetic pulse welding (MPW) is a promising joining technology for the large-scale production of dissimilar metallic joints. Although the heat input is comparatively low, the temporary occurrence of high temperatures in the joining gap was found to play an important role during the joint formation. It is possible that the melting or even the boiling temperature of the involved materials will be exceeded, and fusion welding will occur. The purpose of this study is to investigate the influence of target materials with different thermal properties on the joint formation and weld seam characteristic. Therefore, MPW between steel targets and aluminum flyers was performed with and without copper coatings on steel. The lower melting temperature of copper compared to steel had no significant effect on the appearance of the mixed zones in the interface and the amount of molten target material or aluminum, respectively. Nevertheless, the comparison of the higher impact energies showed, that the copper interlayer can lead to a decrease in the weld length or a degradation of the weld quality due to an extended intermetallic phase formation or cracks. This result is important for the parameter adjustment of magnetic pulse welding processes.

Highlights

The combination of dissimilar materials like steel, aluminum alloy or magnesium alloy within one component is important to implement lightweight design or increase the load capability
The necessary pressure can be applied by a high-speed impact as it occurs during explosive welding (EXW), vaporizing foil actuator welding (VFAW), laser impact welding (LIW) or magnetic pulse welding (MPW) [1,2]
The polished beginning cross sections were analyzed by optical microscopy to determine the belower energy level, the influence of the copper interlayer on the weld formation is small

Summary

Introduction

The combination of dissimilar materials like steel, aluminum alloy or magnesium alloy within one component is important to implement lightweight design or increase the load capability. Conventional fusion welding technologies for welding of materials within one material group, e.g., different steels, are often not applicable for dissimilar material combinations due to the huge differences in thermo-physical properties, e.g., the melting temperatures as well as the formation of brittle intermetallic phases. The application of pressure welding technologies offers the reduction of the heat input and, can avoid the formation of critical intermetallic phases. MPW is based on the electromagnetically driven high-speed forming operation of a workpiece (flyer), followed by the oblique collision with a stationary joining partner (target). It is suitable for the large-scale production of parts with a limited wall thicknesses of a few millimeters [3]. The charging voltage of the capacitors in the pulse generator is one of the key parameters to adjust the energy input [4]

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