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A quantitative phase-field approach for multiphase systems that is based upon CALPHAD free energies is used to model the aluminization of nickel wires, wherein vapour-phase alloying is used to deposit Al on the surface of the Ni wire and then the wire is annealed so that to remove all Al gradients and achieve a homogenous Ni-Al alloy. Both processes are modelled and numerical results are compared with experiments. It is found that the kinetics of both processes is controlled by bulk diffusion. During aluminization at 1273 K, formation and growth of intermetallics, Ni2Al3NiAl and Ni3Al, are strongly dependent on the Al content in the vapour phase. Ni2Al3growth is very fast compared with NiAl and Ni3Al. It is also found that an intermediate Al content in the vapour phase is preferable for aluminization, since the Ni2Al3coating thickness is difficult to control. Ni2Al3is found to disappear in a few minutes during homogenization at 1373 K. Thereafter, the NiAl phase, in which the composition is highly non-uniform after aluminization, continues growing until the supersaturation in this phase vanishes. Then, NiAl coating disappears concomitantly with the growth of Ni3Al, which disappears thereafter. Finally, the Al concentration profile in Ni(Al) homogenizes. [ABSTRACT FROM PUBLISHER]

The experimental measurement of the evolution of interfaces in three dimensions is reviewed, concentrating on the evolution of polycrystalline and solid-liquid systems, including growth and coarsening in dendritic systems and evolution during liquid-phase sintering. Both ex situ destructive techniques and in situ nondestructive techniques are considered. The importance of making three-dimensional measurements that can be quantified and unambiguously compared with theory is discussed, showing that these measurements provide a direct validation of theory and critical initial conditions for simulations. [ABSTRACT FROM AUTHOR]

We analyze the development of compositional and surface nonuniformities during the growth of strained alloy films, for the case of different surface mobilities of the alloy components. We find that a difference in surface mobilities can completely suppress the stress-driven morphological instability. The stabilization occurs under compressive misfit when one atomic species is both large and fast relative to the other, and similarly under tensile misfit when one species is small and fast. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]