Recently, a dislocation model that quantitatively related the minimum grain size obtainable by milling, dm, to several physical parameters, such as the activation energy for self-diffusion and the stacking fault energy, in a nanocrystalline material was developed. The development of the model was based on the suggestion that the minimum average grain size, dm, was the result of a balance between the formation of dislocation structure and its recovery by thermal processes. The predictions of the above model were found to be in good agreement with experimental data and trends reported for nanocrystalline face-centered cubic and nanocrystalline body-centered cubic metals. Here, the validity of the model for the description of the behavior of nanocrystalline hexagonal close-packed metals for which data on the minimum grain size, dm, were available was examined. Also, the general applicability of the model to other severe plastic deformation processes was considered.

Correlation between the Behavior of Nanocrystalline HCP Metals and the Dislocation Model for the Minimum Grain Size Obtainable by Milling. F.A.Mohamed: Materials Science and Engineering A, 2010, 527[9], 2157-62