冷喷涂单颗粒铜在铝基体上的显微结构研究

Microstructure of Copper Particle Deposited on Aluminum by Cold Spray

采用冷喷涂法在铝(Al)基体上沉积单颗粒铜(Cu),利用聚焦离子束/电子束(FIB/SEM)系统精确定位并原位制备了完整单个颗粒Cu沉积在Al基体上的透射样品,分析其显微结构及形成原因。实验结果表明,撞击过程中温度与应力分布不均匀,导致沉积Cu颗粒不均匀形变。Cu/Al界面受影响较大:颗粒动能转化为形变能和热能,打破了界面处氧化膜,使界面附近温度迅速升高,发生动态再结晶,生成金属间化合物Cu_9Al_4;Cu颗粒内距界面越远的区域,受温度和应力的影响越小,其变形主要是通过晶体内位错增殖和移动;沉积颗粒顶部,远离Cu/Al界面,几乎不受应力和温度影响,保持原始显微结构。

The aim of the paper is to explore the deformation mechanism of particles in cold spray. Focused ion beam/scanning electronic microscopy（FIB/SEM） system was employed to prepare a TEM specimen of a whole copper particle on aluminum substrate on wipe test. Through analyzing the microstructure of the TEM sample, the result indicates that the inhomogeneous deformation of Cu particles is due to the inhomogeneity of stress field and temperature. During the impact, the kinetic energy of particles transforms to deformation energy and heat, which breaks the alumina layer and increases the temperature quickly. Because of high temperature and strain rate, re-crystallization happens in Cu near the interface and intermetallic compound Cu9Al4 is obtained on the interface. The farther the grains are from the interface, the less the influence on them. Heat or stress field have little effect on the grains far away from the interface, especially on the top of particle.