Kinematic hardening in a dispersion strengthened aluminum alloy: experiment and modeling

The hardening behavior of a dispersion strengthened aluminum alloy, 8009, i s characterized experimentally and shown to be primarily kinematic in natur e. Although the alloy contains 0.25 volume fraction of dispersoid, the micr ostructure is analogous to that of a material cycled to saturation in fully reversed loading fatigue in that it consists of essentially dislocation an d dispersoid free grain interiors with a grain diameter of less than 0.5 mu m. The high dispersoid volume fraction is associated with the grain bounda ries. An attempt is made to model the hardening behavior of the alloy using the micro-mechanic model known as the generalized method of cells (GMC). G ood correspondence between the model response and the actual material behav ior is obtained; however, matching of flow stresses between model outputs a nd actual alloy behavior requires assignment of unrealistically high materi al properties to some model subcells. Explanations for the limited modeling success are tendered and suggestions for improvement of the physical reali sm of the GMC model are proposed. (C) 2000 Elsevier Science S.A. All rights reserved.