The work hardening model developed over the last five years by Nes, Marthinsen and co-workers has been further developed in order to deal with work softening phenomena and handle the transient deformation that is obtained from FEM calculations of rolling and extrusion. In relation to the phenomenon of work softening during cold rolling it is demonstrated that the key microstructural feature relates to the evolution in sub-boundary misorientation. It is further demonstrated that the model is capable of predicting, for the first time, softening during foil rolling of an AA8xxx-alloy in a quantitative manner. The problems associated with predicting the substructure evolution under transient conditions have been addressed for the case of loading in creep and for an example of material flow during extrusion.