Grain size dependence of the plastic deformation kinetics in Cu

Data on the effect of grain size d in the range of nm to mm on the plastic deformation kinetics of Cu at 77-373 K are analyzed to determine the influence of grain size on the strain rate-controlling mechanism. Three grain size regimes were identified: Regimes I (d approximate to 10(-6) -10(-3) m), II (d approximate to 10(-8) -10(-6) m) and III (d < similar to 10(-8) m). A dislocation cell structure characterizes Regime 11, which no longer occurs in Regime II. The absence of all intragranular dislocation activity characterizes Regime III. The following mechanisms were concluded to be rate-controlling for epsilon approximate to 10(-5) -10(-3) s(-1) : (a) Regime I, intersection of dislocations; (b) Regime I, grain boundary shear promoted by dislocation pile-ups; and (c) Regime III, grain boundary shear. The major effect of grain size on the intersection mechanism in Regime I is on the mobile and forest dislocation densities; the effect in Regime 11 is on the number of dislocations and on the number of grain boundary atom sites; the effect in Regime III is on the number of grain boundary atom sites. The transition grain size from one regime to another depends on the strain rate and temperature. Crystallographic texture is also important. (C) 2002 Elsevier Science B.V. All rights reserved.