On the nature of high internal stresses in ultrafine grained materials

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We present a model to account for high internal elastic strains ultra-fine grained materials. The model is based on the concept of highly nonequilibrium grain boundaries containing random extrinsic grain boundary dislocations (EGBDs) networks. Root mean square elastic strain calculated on the basis of this model is in good agreement with experimental data, if reasonable values of EGBD density are assumed. The excess energy of grain boundaries caused by the internal stresses is estimated. The volume expansion of ultrafine grained materials is evaluated by the use of non-linear elasticity approach. The calculated value of the dilatation also agrees well with experimental results reported in the literature. © 1994.

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Nanostructured Materials