Analysis of the TEM Specimen Prepared by FIB of Copper Deposited on Aluminum

 Cold gas dynamic spray (CGDS) is a high-rate material deposition process in which fine solid powder particles are accelerated in a supersonic jet of compressed (carrier) gas to velocities which is higher than critical velocity. Although CDGS has been developed for several decades, there still are some suspicions of bonding mechanism during its process. In order to explore the bonding mechanism of particles depositing on the substrate, focused ion beam/ scanning electronic microscopy (FIB/ SEM) system was employed to prepare a TEM sample of cross-section of single copper particle deposited on aluminum substrate. As a new method of manufacturing, FIB/ SEM system has unexampled virtues compared with the conventional machining tools and thereby has important application in the fields of locally manufacturing TEM specimen. Because of the TEM sample has been prepared by FIB/ SEM that containing the whole single particle which was accurate positioned, its microstructure of different locations could be observed, compared and analyzed. The analysis indicated the adiabatic shear instability plays an essential role during the deposition process. During the collision, the kinetic energy of particles with high velocity transformed to deformation energy and a lot of heat which occurred the temperature increasing in less than 100 ns. The high temperature and the fast deformation led to re-crystallization and appearance of Cu9Al4.

KEY WORDS FIB, TEM, Cu-Al, cold gas dynamic spray (CGDS)