Yang Jingwei, Zhang Jie, Qiao Jian
School of Electromechanical Engineering, Foshan University, Foshan 528000, China.
State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
Materials (Basel). 2019 Jul 19;12(14):2306. doi: 10.3390/ma12142306.
Ultrasonic welding (UW) is an important joining technique in the electrical industry. Molecular dynamic simulation has been shown to possess several advantages for revealing the evolution of the atomic-scale structure and the interpretation of diffusion mechanisms at the microscopic level. However, voids associated with the understanding of microstructure evolution in the weld zone and dynamic processes that occur during ultrasonically welded materials still exist, and no UW studies at the atomic scale have so far been reported. In this study, molecular dynamic simulations of UW between Al and Cu were performed to investigate the diffusion behaviors of Al and Cu atoms. The results confirmed the occurrence of asymmetrical diffusion at the Al/Cu interface during UW. Meanwhile, recovery was noticed in the disordered Al blocks at low temperature. The thickness of the diffusion layer increased with the welding time. For relatively long welding times (1 ns), the concentrations of Al and Cu revealed the appearance of phase transitions. In addition, the diffusion during UW was identified as a dynamic and unsteady process. The diffusion coefficient was much larger than that underwent during the steady diffusion process despite the low interfacial temperature (below 375 K), which was mainly attributed to shear plastic deformation at the interface.
超声焊接（UW）是电气工业中一种重要的连接技术。分子动力学模拟已被证明在揭示原子尺度结构的演变以及微观层面扩散机制的解释方面具有若干优势。然而，与理解超声焊接材料时焊缝区微观结构演变及动态过程相关的空洞仍然存在，并且目前尚未有关于原子尺度超声焊接的研究报道。在本研究中，对铝和铜之间的超声焊接进行了分子动力学模拟，以研究铝和铜原子的扩散行为。结果证实了超声焊接过程中铝/铜界面处存在不对称扩散。同时，在低温下无序的铝块中观察到了回复现象。扩散层的厚度随焊接时间增加。对于相对较长的焊接时间（1纳秒），铝和铜的浓度显示出相变的出现。此外，超声焊接过程中的扩散被确定为一个动态且不稳定的过程。尽管界面温度较低（低于375K），但扩散系数比稳态扩散过程中的扩散系数大得多，这主要归因于界面处的剪切塑性变形。
