Microstructure evolution, slip patterns and flow stress

The development of deformation microstructures in medium to high stacking fault energy fcc metals is reviewed illustrating that the basic microstructural element is a cell block. The elongated cell blocks are defined by extended nearly planar boundaries that lie on special planes and enclose a group of approximately equiaxed cells. This duplex structure persists throughout Stage II–IV. What is known about the origins of these structures and the role of the slip pattern is reviewed. Taking all the measurable structural parameters with respect to the cell blocks: spacing, misorientation angle, and dislocation density, and assuming additive strength contributions, flow stress predictions are derived from Hall–Petch and dislocation strengthening. These predictions are in good agreement with the stress values and hardening rates observed experimentally.