Central to the competitiveness of Rio Tinto Alcan and other aluminum manufacturers, is the quantitative linkage between products and the processes by which they are made. This type of activity has gained attention internationally and there are significant programs underway to develop through process models for various metallurgical fabrication processes. Inherently, the need for these types of models is that the properties of the metal products depend on the microstructure of the material which in turn is a complex function of composition, grain size and orientation, distribution of phases and precipitates and its thermo-mechanical history. The development of a particular microstructure and the desired properties in an industrial process however is less than straightforward because the latter usually involves a complex deformation and temperature path which can be very different through the thickness of the material depending on its location. This book describes the development of a mathematical model and experimental study for the material flow and microstructure changes during extrusion of AA3003 aluminum alloy which is used for manufacturing of automobile heat exchangers.