Mechanical behavior of electrodeposited copper-nickel multilayered thin films

The present work is an investigation of the mechanical properties of copper-nickel thin film superlattices.; Cu-Ni films were fabricated by a potentiostatic-coulometric electrodeposition technique. These films had composition modulation wavelengths ranging from 2-80 nm. The microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The hardness was measured by low load indentation. Interface sliding and acoustic damping tests were performed by a vibrating membrane technique. The films were annealed to reduce the composition gradient at the interface and the reduction in hardness was correlated with the measured interdiffusion. Ni-Al{dollar}sb2{dollar}O{dollar}sb3{dollar} nanocomposites were also fabricated by codeposition of alumina particles, from a nickel sulfamate plating electrolyte, on a rotating disk electrode.; The as-prepared microhardness of superlattices was found to be a function of the wavelength of the composition modulation. The trend for long wavelengths ({dollar}lambda >{dollar} 20 nm) was that the microhardness decreased with increasing wavelength in qualitative agreement with the Hall-Petch relationship. There was a sharp peak in the range of about 12 nm below which the hardness dropped abruptly as the composition modulation wavelength decreased. This drop was correlated with the increase of structural coherence between layers. The hardness was observed to at first increase and then decrease with interdiffusion. After the initial increase the hardness was shown to vary as the 1.1 {dollar}pm{dollar} 0.1 power of the composition modulation amplitude for samples with coherent interfaces.; The biaxial stress as a function of temperature was determined by the frequency of vibration of a multilayered membrane. The results indicate that there was an interfacial relaxation for samples with incoherent interfaces. This was modeled with very good agreement with the experiments by imperfect strain transfer across the interface.; Existing theories cannot quantitatively reproduce the experiments fully. This seems to be due to two considerations. The effect of the interface transition from coherent to incoherent is ignored in the general theories, and because at extremely low wavelengths ({dollar}lambda <{dollar} 5 nm) it is unclear whether normal descriptions of the interaction of a dislocation strain field and compositional variations are valid or whether the classical description of the interface must be modified.; The microhardness of the Ni-Al{dollar}rmsb2Osb3{dollar} nanocomposites was found to increase with codeposited particle density in agreement with dispersion hardening theories. The microhardness was found to be strongly correlated with the rotation speed of the rotating disk electrode. Analysis of the data showed that the submicron diameter alumina particles were incorporated in the deposit according to a simple diffusion model, thus allowing direct prediction of the hardness enhancement as a function of deposition conditions. (Abstract shortened by UMI.)...