Atomic Observation of the Al₂Cu Interface in Cu/Al Shaped Charge Liners

Shaped charge liners have recently received a lot of attention due to their exceptional properties, particularly copper–aluminum (Cu–Al) bimetal liners which cause larger penetration than copper liners. However, inevitably high brittle compositions exist along the interface such as Al₂Cu and Al₄Cu₉ which induce low plasticity to negatively influence the performance. Until now, the interface structure between these compositions and Cu/Al has seldom received attention. In this paper, the interface between Al₂Cu and Cu/Al is depicted and studied on atomic level. Aberration-corrected scanning transmission electron microscopy (STEM) and energy dispersive spectrometry (EDS) reveal that the Al₂Cu are the main compositions of Al_xCu along Cu/Al interface. Importantly, the interface structure of Al₂Cu–Cu and Al₂Cu–Al is demonstrated, where the Al₂Cu–Cu interface has a transition region showing polycrystalline, while the Al₂Cu–Al interface exhibits a sharp boundary which can form a 5 nm width co-exist area in which Al₂Cu and Al both exist without any mismatch or dislocation. The findings certify the discrepant atomic structure in the interface which can help understanding the connection style of highly brittle compositions and Cu/Al. This phenomenon has potential value in understanding the Cu/Al liner's performance and Cu/Al alloys in the future.