Source-limited coarsening

Source-Limited Coarsening. During source-limited coarsening, the interfaces surrounding the particles behave as poor sources and sinks, and the coarsening rate then depends upon the rate at which the diffusion fluxes between the particles can be created or destroyed (accommodated) at the particle interfaces. In a simple model, the same assumptions can be made about the source action at the particles as those that led to Eq. 13.24. The rate of particle growth can then be written... 

Use the simple rate-constant type of formulation employed in Sections 13.4.2 and 15.1.1 to analyze source-limited precipitate growth and particle coarsening, respectively. 

Source/sink-limited coarsening therefore leads to an increase in the mean particle size with the square root of time (f / ). 

If the coarsening process is limited by the rate at which atoms diffuse through the matrix from the source particles to the sink particles, it can be shown [13] that the mean particle size of the distribution will increase with time according to... 

In the present work, steel oxidation by oxygen provided by nickel oxide was identified as the main source for volume expansion and the limited shrinkage of the half-cell multilayer. In addition, intense Cr-Fe-Ni interdiffusion and Ni coarsening were observed when the different materials are co-sintered. The Cr oxide formed on the steel surface at 1000 C seems to limit Ni diffusion through the steel, but it cannot prevent Fe outward diffusion when the temperature is further increased. 

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