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Processing, Microstructure, and Fracture Behavior of Nickel/ Nickel Aluminide Multilayered Thin Films
Published online by Cambridge University Press: 10 February 2011
Abstract
The Ni-Ni3Al system is the basis of a large number of Ni-based superalloys used extensively in the aerospace industry. The mechanical properties of bulk superalloys, which primarily consist of a Ni-based fcc matrix reinforced with cubic precipitates of Ni3Al, have been extensively researched. The goal of the present study is to investigate the mechanical properties of multilayered Ni / Ni3Al nanocomposites in the thin film form. These multilayers have been processed using UHV magnetron sputtering by alternate deposition of pure elemental Ni and Ni-25at%Al layers in the range of 20 nm – 120 nm. By varying the substrate material and processing parameters such as deposition temperature, multilayers with two types of interfacial orientations. (111) Ni //(111) Ni3Al and (002) Ni //(002) Ni3Al have been fabricated. Microstructural and phase characterization of the multilayers in both plan-view as well as cross-section geometries have been carried out using x-ray diffraction, SEM and TEM and the results of these will be discussed. Both orientations exhibited a high density of twins lying on the {111} planes. The loss of coherency in these multilayers as a function of the layer thickness will also be discussed. The cross-section fracture behavior of these multilayers has been studied by SEM fractography. Failure mode for fracture was a result of the application of tensile stresses. Interesting effects of the interfacial orientation and the layer thickness on the fracture surface of these multilayers will be discussed.
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- Copyright © Materials Research Society 2000