Abstract
Magnetic pulse welding (MPW) is often categorized as a cold welding technology, whereas latest studies evidence melted and rapidly cooled regions within the joining interface. These phenomena already occur at very low impact velocities, when the heat input due to plastic deformation is comparatively low and where jetting in the kind of a distinct material flow is not initiated. As another heat source, this study investigates the cloud of particles (CoP), which is ejected as a result of the high speed impact. MPW experiments with different collision conditions are carried out in vacuum to suppress the interaction with the surrounding air for an improved process monitoring. Long time exposures and flash measurements indicate a higher temperature in the joining gap for smaller collision angles. Furthermore, the CoP becomes a finely dispersed metal vapor because of the higher degree of compression and the increased temperature. These conditions are beneficial for the surface activation of both joining partners. A numerical temperature model based on the theory of liquid state bonding is developed and considers the heating due to the CoP as well as the enthalpy of fusion and crystallization, respectively. The time offset between the heat input and the contact is identified as an important factor for a successful weld formation. Low values are beneficial to ensure high surface temperatures at the time of contact, which corresponds to the experimental results at small collision angles.
Highlights
Dissimilar metal welding plays an important role in the fabrication of multi-material parts.Materials with different mechanical, physical, or chemical properties need to be joined in order to fulfill the requirements of lightweight structures and high endurance parts or to save costs
The time-dependent course of the light with emission was measurement system described previously. It was triggered by the current signal of the generator, measured with the flash measurement system described previously [22]
If the cloud of particles (CoP) travels faster than the collision point, the waiting time is increased in the abstracts the effects in the moving interaction zone of a real magnetic pulse welding (MPW) process
Summary
Dissimilar metal welding plays an important role in the fabrication of multi-material parts. Special interlayers are applied during EXW to avoid excessive intermetallic phase formation, see [7] Another possibility is to reduce the “levels of temporal and force parameters required for joint formation” if the temperature of the near-contact layer of the welded materials is too high. Additional energy from an exothermic reaction between the joining partners or interlayers is beneficial for the joint formation, if well-adjusted [18] This underlines the influence of thermal effects in MPW and the need for a comprehensive model or at least the identification of the most relevant input variables for heating and cooling of the surfaces and the interface. Build up a temperature model for the welding interface, based on the heat input by the CoP
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