Equal-channel angular pressing was used to refine the grain sizes of pure Al and an Al-3wt%Mg alloy containing minor additions of Sc or Zr. Following the equal-channel angular pressing, the grain sizes were in the ultra-fine sub-micron range. Diffusion couples were prepared from the fine-grained material produced by equal-channel angular pressing and from coarse-grained material without equal-channel angular pressing. These couples were used to measure the interdiffusion coefficients of Mg in an Al lattice. The results showed that the interdiffusion coefficient was larger in the fine-grained material and that the experimental data from this couple agreed with the predictions of molecular dynamic simulations performed using the embedded-atom method. An activation energy of about 87kJ/mol was estimated for the grain-boundary diffusion of Mg in Al. This value was consistent with that expected from measurements of the activation energy for the lattice diffusion of Mg in Al. There was no evidence of enhanced diffusion in the boundaries produced by equal-channel angular pressing due. It was suggested that this was due to rapid equilibration of the non-equilibrium boundaries at high temperatures.

Characteristics of Diffusion in Al-Mg Alloys with Ultrafine Grain Sizes. T.Fujita, Z.Horita, T.G.Langdon: Philosophical Magazine A, 2002, 82[11], 2249-62