Tribological and mechanical behavior of nanostructured Al/Ti multilayers

Al/Ti nanostructured metallic multilayers (NMMs) with individual layer thicknesses of 2.5 and 30 nm were sputter-deposited on Si substrate. The mechanical and tribological properties of the Al/Ti NMMs were studied by nanoidentation and nanowear tests. Microstructures of the NMMs were characterized using X-ray diffraction, scanning electron microscopy, electron backscattered orientation mapping, and transmission electron microscopy before and after the tests. Decreasing the layer thickness from 30 to 2.5 nm led to an increase of hardness from 3.13 to 4.94 GPa. For both NMMs, the wear rate increased with applied load and decreased with hardness. Nanoindentation tests on the worn surface revealed significant work hardening of the subsurface material. The deformation mechanisms of NMMs were found to strongly depend on layer thickness and interface structure. (C) 2015 Elsevier B.V. All rights reserved.