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

The hardening behavior of a dispersion strengthened aluminum alloy, 8009, is characterized experimentally and shown to be primarily kinematic in nature. Although the alloy contains 0.25 volume fraction of dispersoid, the microstructure is analogous to that of a material cycled to saturation in fully reversed loading fatigue in that it consists of essentially dislocation and dispersoid free grain interiors with a grain diameter of less than 0.5 μm. The high dispersoid volume fraction is associated with the grain boundaries. 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). Good correspondence between the model response and the actual material behavior is obtained; however, matching of flow stresses between model outputs and actual alloy behavior requires assignment of unrealistically high material properties to some model subcells. Explanations for the limited modeling success are tendered and suggestions for improvement of the physical realism of the GMC model are proposed.