As an interlayer in the gradient layers such as AIN/Ti/TiN/DLC prepared by plasma-based ion implantation (PBII) on 20241 aluminum alloy, titanium layer plays an important role in enhancing adhesion. reducing thermal stress. limiting the crack propagation, etc. A series of dual-layers prepared by PBII with nitrogen then titanium at various sputtering currents of titanium target on 2024 aluminum alloy have been reported in this paper. The composition distributions and the chemical states are analyzed using X-ray photoelectron spectroscopy (XPS). The structures are studied with grazing X-ray diffraction (GXRD). The results show that PBII with titanium strongly depends on the sputtering current. It is found that there exists a critical sputtering cur-rent corresponding only to a titanium-implanted layer containing TiAl3. When the sputtering current exceeds the critical value. a titanium-deposited layer rich in alpha-Ti is formed on a titanium-implanted layer. By controlling the sputtering current an appropriate titanium interlayer can be prepared to meet the requirement of forming a proper gradient layer. (C) 2004 Elsevier B.V. All rights reserved.