Plastic deformation and microstructures evolution in pure copper ultrasonic welding
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Graphical Abstract
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Abstract
The formation process of ultrasonic welding of pure copper joints was determined by Interfacial plastic deformation and grain evolution. However, the understanding of the welding mechanism is still unclear. In this work, a three-dimensional finite element model of pure copper ultrasonic welding is established to investigate the welding temperature field and plastic strain distribution. Secondly, the predicted temperature and plastic strain results are used as the initial condition, and combined with the theory of dynamic recrystallization. Finally, the dynamic recrystallization process and the growth of the grain in the welding were simulated by the finite element method and the cellular automata method, respecitively. The results show that the irregular distribution of grain leads to the obvious difference between the plastic strain of the material under the welding interface and the materials beneathe the sonotrode and above the anvil. The materials near the sonotrode and anvil tips have generated a utra-fine grain that suffers dynamic recrystallization. After welding time of 0.19 s, the dynamic recrystallization is generated in the entire welding area, and the process of dynamic recrystallization of the upper specimen should be longer than of the lower specimen. The corse grains are distributed at the copper side of the sonotrode/Cu interface, while the finer grains are distributed at the welding interface. The distribution of simulated plastic deformation is basically the consistance with the distribution of experimental vicker's hardness. In addition, the simulated grains is basically in line with the test. These demonstrate that plastic deformation and grain evolution in pure copper ultrasonic welding were successful simulated.
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