Measurement of Collision Conditions in Magnetic Pulse Welding Processes

MPW （magnetic pulse welding） is a solid state joining technology that allows for the generation of strong metallic bonds, even between dissimilar metals. Due to the absence of external heat, critical intermetallic phases can largely be avoided. In this process, Lorentz forces are utilized for the rapid acceleration of at least one of the two metallic joining partners leading to the controlled high velocity impact between them. The measurement of the collision conditions and their targeted manipulation are the key factors of a successful process development. Optical measuring techniques are preferred, since they are not influenced by the prevalent strong magnetic field in the vicinity of the working coil. In this paper, the characteristic high velocity impact flash during MPW was monitored and evaluated using phototransistors in order to measure the time of the impact. The results are in good accordance with the established PDV （photon Doppler velocimetry） and show a good repeatability. Furthermore, the collision front velocity was investigated using adapted part geometries within a series of tests. This velocity component is one of the key parameters in MPW; its value decreases along the weld zone. With the help of this newly introduced measurement tool, the magnetic pressure distribution or the joining geometry can be adjusted more effectively.

Comparison of Magnetic Pulse Welding with Other Welding Methods

The paper explains the comparison of magnetic pulse welding method which belongs to non-conventional machining methods with other conventional and non-conventional welding methods which include brazing, explosive welding, ultrasonic welding, tungsten and metal inert gas and roll bonding. Magnetic pulse welding differs completely in technology when compared with conventional welding processes because the process is done with high velocity and without heat or consumable materials. It is better than other methods because it＇s cold process and can be done without any heat affect zone. In addition, there is no need for rework and post welding cleaning and there is no scrap problem. Magnetic pulse welding is a green process used to design and build light structure with high strength to reduce the weight and the energy. Magnetic pulse welding reduces the risk of corrosion by limiting the metallic interaction to just the two metals welded; therefore, it replaces the brazing method. Also, it is better than the explosive welding method because there is no risk of handling the explosive material and there is no noise. The part assembly by magnetic pulse welding is stronger than the parts assembly by tungsten and metal inert gas welding and it is easy to achieve a good aesthetic with high speed. Therefore, using magnetic pulse welding technology will not affect the environment.

Interface Microstructure of Al-Fe Tubes Joint by Magnetic Pulse Welding

Magnetic Pulse Welding(MPW)is a very high speed process which produces solid-state welds.In this work, Welding interface microstructure of Al/Fe tubes by MPW and its influence factors were investigated.The equipment with a capacitor of 100 μF was used under different voltages range from 8 kV to 15 kV.SEM and TEM observation were carried out to investigate microstructure of the welding interface.The results show that the dissimilar tubes(Al/Fe)could be welded with the optimum tapered angle of about 4 degree.The welding interface in Al/Fe joints exhibits a characteristic wavy morphology with wavelength of about I00 μm.A new layer exists between base tubes consisting of AI and Fe elements.Ultrafme grained microstructure is founded near the welding interface.The results obtain in this work provide the fundamentals for the investigation of MPW mechanism of dissimilar tubes.

Measurement and analysis technologies for magnetic pulse welding： established methods and new strategies

Magnetic pulse welding （MPW） is a fast and clean joining technique that offers the possibility to weld dissimilar metals, e.g., aluminum and steel. The high-speed collision of the joining partners is used to generate strong atomic bonded areas. Critical brittle intermetallic phases can be avoided due to the absence of external heat. These features attract the notice of industries performing large scale productions of dissimilar metal joints, like automo- tive and plant engineering. The most important issue is to guarantee a proper weld quality. Numerical simulations are often used to predict the welding result a priori. Nevertheless, experiments and the measurement of process parameters are needed for the validation of these data. Sensors nearby the joining zone are exposed to high pressures and intense magnetic fields which hinder the evaluation of the electrical output signals. In this paper, existing analysis tools for process development and quality assurance in MPW are reviewed. New methods for the process monitoring and weld characterization during and after MPW are introduced, which help to overcome the mentioned drawbacks of established technologies. These methods are based on optical and mechanical measuring technologies taking advantage of the hypervelocity impact flash, the impact pressure and the deformation necessary for the weld formation.

Effects of Standoff Distance on Magnetic Pulse Welded Joints Between Aluminum and Steel Elements in Automobile Body

In industrial production,the standoff distance of magnetic pulse welding(MPW)is a critical parameter as it directly affects welding quality.However,the effects of standoff distance on the physical properties of MPW joints have not been investi-gated.Therefore,in this study,aluminum alloy(AA5182)sheets and high-strength low-alloy steel(HC340LA)sheets were welded through MPW at a discharge energy of 20 kJ,under various standoff distances.Thereafter,mechanical tests were performed on the MPW joints,and the results indicate that there is a significant change in the shear strength of the AA5182/HC340LA-welded joints with respect to the standoff distance.When the standoff distance ranges from 0.8 to 1.4 mm,the strength of the joint is higher than that of the base AA5182 sheet.Microscopic observations were conducted to analyze the interfacial morphology,element diffusion behavior,and microdefects on the welding interface of the AA5182/HC340LA joints.The AA5182/HC340LA joint with a standoff distance of 1.4 mm possesses the longest welded region and the largest interfacial wave.This interfacial wave pattern is suitable for achieving MPW joints with high shear strengths.