DIFFUSION AND PHASE NUCLEATION IN METALLIC MULTILAYERS

Possible structural changes in multilayers are: interdiffusion, interfacial reaction, transformation of one phase, and coarsening of the layering. Types of diffusion experiment using multilayers are reviewed. In systems with a marked diffusional asymmetry, the interdiffusivity is greatly reduced by stress effects which can be quantitatively modelled. A new technique is demonstrated, which uses neutron reflectometry to determine self-diffusivities. The kinetics of growth of an interfacial product phase are reviewed, and an explanation is given for the nucleation barriers found in the presence of strong driving forces. The main factors in phase selection are outlined.