Subgrain size in view of the composite model of dislocation structure

The polygonized subgrain structure of plastically deformed metals is treate d as a heterogeneous dislocation structure in terms of the composite model, and relations of the mean subgrain size to the total dislocation density a nd to the applied stress are investigated. The analysis supports the simple proportionality between the subgrain size d and the reciprocal applied str ess sigma, i.e., d = KGb/sigma (K is a constant, G the sheer modulus, and b the magnitude of the Burgers vector), corresponding to the principle of si militude. It suggests an interpretation of the highly dispersed values of K in different materials as a result of an influence of several parameters. The proportionality factor between d and rho (-1/2) (rho is the total dislo cation density) depends on the volume fraction of hard regions f(H) and tak es into account that substructures with the same subgrain size can store di fferent dislocation densities. (C) 2001 Elsevier Science B.V. All rights re served.