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Relative grain boundary energy as a function of misorientation angle was measured in a cube-oriented, 120 µm-thick Al foil and in a <111> fiber-textured, 1.7 µm-thick Al film using a multiscale analysis of the grain boundary dihedral angles. For the Al foil, the energies of low-angle boundaries increased with misorientation angle, in good agreement with the Read-Shockley model. For the Al film, two energy minima were observed for high-angle boundaries. Grain growth was studied in 25 and 100 nm-thick films that were annealed at 400 °C for a series of times in the range of 0.5 to 10 h. For the 100 nm-thick film, grains approximately doubled their size (equivalent circular diameter) before grain growth stagnated. The steady-state distributions of reduced grain area for two-dimensional, Monte Carlo Potts and partial differential equation based simulations showed excellent agreement with each other, even when anisotropic boundary energies were used. However, the simulated distributions had fewer small grains than the experimental distributions.

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Abstract: Quantitative X-ray mapping in the analytical electron microscope (AEM) could improve the statistics of grain-boundary segregation measurements if high spatial resolution can be maintained at lower magnifications (<500 kX). Typically, only about 10 boundaries are analyzed because of the difficulty of conventional AEM measurements; however, a low-magnification quantitative X-ray map could contain twice this number of boundaries in a single field of view. Microscope conditions and mapping parameters have been explored for operation at ∼250 kX, under a variety of conditions to illustrate the trade-offs between various characteristics, such as analytical resolution, counting statistics, magnification, and acquisition time. From these data, it is possible to extrapolate to maps generated under different conditions and estimate their limitations with respect to these characteristics. A simple model has been developed to describe the behavior of inclined grain boundaries that can be used to estimate the detectability of segregant as a function of boundary tilt. Using quantitative X-ray maps, grain boundary Cu coverage has been measured from 55 boundaries in Al–4 wt.% Cu with minimal user effort. For fine-grained thin films, mapping is substantially more efficient than other methods of data acquisition and may be used to measure segregation at large numbers of boundaries.

The structure of electrodeposited composite coatings of Ni–Al–Al2O3, with Ni as the matrix and Al and Al2O3as second‐phase particles, was investigated using light microscopy and scanning electron microscopy. Ni coatings with no particles, which were used as reference samples, had progressively coarser structures with increasing current density. Co‐deposition with Al resulted in refinement of the Ni matrix structure at high (>10 A dm−2) current densities. For single‐particle baths, the co‐deposition of Al2O3was more strongly affected by current density and bath particle content than was the co‐deposition of Al. However, for baths containing both Al and Al2O3the amount of incorporated Al2O3no longer depended on current density. With the choice of appropriate conditions, coatings of Ni with up to 39 vol.% Al2O3were made. Similar experiments with Al yielded a maximum of 17.5 vol.% only. Uniform and graded mixed‐particle coatings were also produced. When coatings containing Al were annealed, the reaction of the two elements resulted in the formation of either single‐phase γ or two‐phase γ–γ′ alloys, in agreement with the equilibrium phase diagram.

Metal matrix/metal particle composite coatings were deposited, heat treated and characterized. A nickel matrix/aluminum particle coating deposited from a sulfamate bath was chosen as a model system. By varying the process parameters, up to approximately 20 vol. % Al particles were incorporated into the coatings. Based on light optical and scanning electron microscopy, a schematic model is presented for coating morphology development during codeposition of small, electrically conductive particles. For high deposition current densities, the hardness of the as-plated Ni-Al coating was higher than that of pure Ni coatings due to the nucleation and growth of small Ni grains on the surface of the Al particles. This structural refinement leads to Vicker's hardness of about 350–400 HVN (25 g load) for NiAl coatings compared to about 200–250 HVN (25 g load) for pure Ni coatings deposited under similar conditions.

We examine quantitatively the impact of heterogenous nucleation on the temporal evolution of a phase transformation with particular emphasis on the correlation of nucleation site distribution and product phase microstructure. This is accomplished by investigating the spatial correlations in the transforming system via the calculation of several non-equilibrium,n-point correlation functions and thereby defining associated transformation fractions and correlation lengths. Computer simulations of transformations are also employed in order to validate the theoretical description and to relate the microstructural features of the evolving phase to relevant length and time scales in the problem. Finally, our findings are related to the results of experimental calorimetric studies of phase formation in thin films.

Ni/Al multilayer films with 1:3 molar ratio and periodicities in the range 640–2000 nm were prepared by sputter deposition, and investigated by differential scanning calorimetry and X-ray diffraction. X-ray diffraction showed that only NiAl3 formed in the reaction of these films. The calorimetry measurements were analyzed using one-dimensional diffusion-controlled growth kinetics. The activation energies so obtained were in the range 1.64–1.76 eV, and the pre-exponential factors were (5–50)×10−4 m2s−1. These kinetic growth parameters were extracted from the calorimetry data using a variety of analysis methods applied to constant-heating-rate calorimetry data. Good agreement was found among the results of the various methods. The present paper, in addition to providing the kinetic parameters for the growth of nickel trialuminide in these Ni/Al films, demonstrates the general utility of multilayer films and calorimetric methods in the determination of the growth kinetics of intermetallic phases in diffusion couples.

Abstract: Solid state reactions of sputter-deposited Nb/Al multilayer thin films, with periodicities in the range 10–333 nm, have been studied by differential scanning calorimetry. The first phase to form upon annealing the films in NbAl3. Constant-heating-rate calorimetric measurements show the presence of two peaks for the formation of this phase, while isothermal scans reveal that the first peak is associated with a nucleation and growth type transformation. The formation of NbAl3 is thus interpreted as a two-stage process of nucleation and growth to coalescence (first peak) followed by growth until the consumption of one or both reactants (second peak).

Abstract: In this paper, we examine, both experimentally and theoretically, the kinetics of formation and microstructure of product phases in thin film reactions, using the Nb/Al and Ti/Al systems as our prototypes. The results of calorimetry and microscopy studies are interpreted using simple kinetic and morphology models. In particular, the kinetic models employed here focus on the nucleation and growth components of the phase formation process and the morphology models provide a starting point for the classification of product grain structures.

A study of reactive phase formation in thin films requires the understanding of the thermodynamics and kinetics of the reactions. Previous investigations of phase formation in Nb/Al multilayers using calorimetry and x-ray diffraction have observed that despite the presence of rather large driving forces for phase formation, a pronounced nucleation event occurs. This behavior has been reported in other systems including Ti/Al and Ni/Al. The initial nature of the interface can affect the nucleation, therefore careful studies of the structure and composition of the initial interfacial region may explain the reason for a kinetically separated nucleation and lateral growth step preceding normal phase growth. In addition, examination of the interface may also lend insight into the effects of different deposition processes and can provide evidence for the formation of solid solutions or compounds that can lower driving forces available for phase formation. Finally, the cross-sectional multilayer sample provides a means of characterizing spatial resolution and isolating specimen preparation artifacts.

A typical microprocessor chip has several million devices patterned into it and, as fabrication techniques improve, device dimensions continue to shrink. This miniaturization results in a corresponding decrease in the dimensions of the interconnects between devices, causing an increased susceptibility to failure by current-induced mass transport, or electromigration (EM). It is well known that the addition of a small amount of Cu to Al interconnects increases their median time to failure profoundly. Since EM in these films occurs almost exclusively at grain boundaries, the simplest explanation for the role of Cu is that it segregates to the grain boundaries and reduces their diffusivity. Analytical electron microscopy studies have shown that Cu segregates to grain boundaries in Al under the proper conditions, and its concentration was measured using X-ray energy dispersive spectroscopy (EDS), but only a small number of boundaries were measured.In order to determine whether the distribution of Cu affects the resistance of a material to EM damage, it is first necessary to characterize the Cu content of the material as a whole, which requires the analysis of large numbers of boundaries rather than just a few.

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