Magnetic pulse welding (MPW) which is one of the impact welding methods is suitable for a wide variety of combinations of similar and dissimilar metals. The flyer plate is accelerated by electromagnetic force and collided to the parent plate. A characteristic wavy interface is formed. The impact velocity and impact angle of the flyer plate during impact are important parameters which affect the interface morphology. In the case of dissimilar metals (e.g. Al/Cu, Al/Fe), the intermediate layer (such as intermetallic compound (IMC)) is formed by wavy interface formation and local temperature increase. The intermediate layer often decreases the bonding strength. Wavy interface formation mechanism and temperature increase at the joint interface should be investigated in order to obtain the dissimilar metal joint with high bonding strength. In this study, the impact velocity and impact angle of the flyer plate were obtained by using ANSYS Emag-Mechanical. Based on the obtained impact velocity and impact angle of the flyer plate in the MPW, the wavy interface formation and temperature change were reproduced by using ANSYS Autodyn for solving non-liner dynamics problems. Al sheets and Cu sheets were joined by the MPW. The joint interface was observed by OM and SEM and compared to the simulation result.
The impact welding was performed for several kinds of metal plate couples. The joint interface exhibited a sinusoidal wave form when two metal plates with the same or similar density (e.g.Al/Al, Cu/Cu and Cu/Ni) were impact-welded by high-speed oblique collision. In contrast, as for dissimilar metal plate couples with large density difference such as Al/Cu, an asymmetric wavy interface was obtained. In order to make clear the reason for morphological difference, a computer simulation of the collision behavior was performed using SPH (Smooth Particle Hydrostatic) method. The simulation results revealed that the wave form was controlled by the interaction between the emitted metal jet and metal plate surfaces ahead of the collision point. For Al/Al and Cu/Ni, the emitted metal jet hit each surface alternatively and this resulted in symmetrical wavy interface formation. While, for Al/Cu, the metal jet was emitted to the direction parallel to the Cu plate, and the interaction took place between the metal jet and the Cu plate surface. The metal jet emission and wavy interface formation mechanism were also investigated.
Joining process and wavy interface formation behavior in explosive welded Cu/Al joints were investigated both numerically and experimentally. First, detonation of the explosive was simulated by Euler-Lagrange coupling method. Change in impact velocity and impact angle at the collision point during detonation was examined using a series of gauge points. Secondly, the numerical analysis of wavy interface formation was performed by using Smoothed Particle Hydrodynamics (SPH) method under the obtained impact velocity and impact angle conditions. The metal jet emission and wavy interface formation were clearly reproduced by the simulation. The Cu/Al lap joints were also fabricated by the explosive welding under the same condition. Microstructure observation revealed that the wavy interface including the intermediate phase layer was formed. The simulation results (wave amplitude and wave length) showed a good quantitatively agreement with the experimental results.
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