Alloy composition and microstructure control in relation to mechanical working for aluminium alloys

Abstract

Two examples of the opportunities for control presented by the rolling process are given. For common alloy sheet, it is shown that composition control and control of the microstructural changes occurring during the processing are necessary in order to obtain the correct combination of texture and grain size needed to produce the forming characteristics ultimately required. In the case of strong alloy plate, the relationships between choice of composition, homogenization, and hot-rolling conditions are discussed together with the underlying intentions of current experimental processes which combine, in different ways, various thermal and mechanical treatments. Finally, examples of the Al-Mg-Si medium-strength alloys are used to illustrate microstructural control through the extrusion process, where the need for maximum productivity and a high standard of surface finish are factors at least as important as final wrought properties in choosing the correct process variables. Possible future changes in fabrication practice to exert greater control over microstructure are discussed, indicating in which areas the most research is currently being carried out.