Strengthening mechanism of super-hard nanoscale Cu/Al multilayers with negative enthalpy of mixing

Q Zhou and S Li and P Huang and KW Xu and F Wang and TJ Lu, APL MATERIALS, 4, 096102 (2016).

DOI: 10.1063/1.4962146

We present unusual high hardness (up to 7.7 GPa) achieved in Cu/Al multilayers relative to monolithic Cu and Al films (similar to 2 GPa and similar to 1 GPa, respectively). Nanotwins and stacking faults (SFs) were proposed to be the main contributors of hardness enhancement, especially when h < 5 nm. Using molecular dynamics simulations of deposition, we demonstrated that intermixing near Cu/Al interface was paramount in stabilizing the SFs in both Cu and Al layers. Our experimental results indicated that the high strength caused by layer intermixing was in sharp contrast to the general belief that only sharp interface structures could strengthen the multilayers. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license.

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