Precipitation strengthening in nanocomposite Cr/Cu–Cr multilayer films

Abstract

Precipitation strengthening in nanostructured metallic multilayer (NMM) films of Cr/Cu–Cr was studied using nanoindentation and electron microscopy. Magnetron-sputtered NMM films having layer thicknesses of 10, 20 and 30 nm were prepared at room temperature (RT) and 100 °C. Some of the RT-deposited films were annealed at 100 °C for 30 min. Cr was introduced in the Cu–Cr layers by using a Cu–Cr target (95 at.% – 5 at.%) target. A significant increase in nanoindentation hardness was observed in the Cr/Cu–Cr. A reduction of hardness dependence on layer thickness was also observed in the Cr/Cu–Cr, such that sample having a layer thickness of 30 nm provides the equivalent strength of a 10/10 nm Cr/Cu. Uniformly distributed Cr particles in the Cu–Cr layers are key strengthening features in these new Cr/Cu–Cr NMM films. A single dislocation-based model was used to correlate the observed mechanical behaviours and microstructure. The model predicts similar trend observed from the experimental results, suggesting that the higher strength in Cr/Cu–Cr is likely the result of dislocation movement impediment due to Cr precipitates in the Cu–Cr layers.

Keywords:

• nanoindentation
• precipitation
• nanocomposites
• TEM

Funding

This work was supported by the US Department of Energy, Office of Basic Energy Science [grant number DE-FG02-07ER46435]. All the NMM samples were deposited at the Center for Materials Research (CMR) Microfabrication Cleanroom Service Center at Washington State University. TEM examinations described in this work were performed at the Franceschi Microscopy and Imaging Center at Washington State University.