The deformation models needed by the aluminium industry

Abstract

Aluminium is a readily deformable metal and, even when alloyed to achieve acceptable engineering mechanical properties, retains sufficient malleability to allow deformation processing, hot and cold, into thin or complex shapes by rolling, extrusion or forging. The world now takes for granted aluminium foil, thin section extrusions and aerospace forgings, each of which was a marvel in its day, and each of which has required much empirical work to define the process route to achieve acceptable mechanical properties and, hence, it is assumed, microstructure. Indeed, the very complexity of many shapes in aluminium has largely hindered the use of any simulation technique to help optimize these products, including modelling, until very recently. Even now, the tortuous strain path followed, for example, by a volume element undergoing extrusion through a port–hole die even defies analysis, let alone simulation, and empiricism must reign. For the more simple geometries of rolling and, to some extent, forging, these more clearly constrained strain paths allow closer analysis, simulation and, albeit at the early stages, modelling, of the development of microstructure and properties in the cold–rolled or hot–rolled state. This paper considers the needs of the aluminium industry, as defined by the end–product (customer) requirements. Predicting the development of the deformed state, in terms of the driving force for subsequent recrystallization and microstructure and crystallographic texture development during deformation, will be considered, together with the subsequent control of annealed structure and properties, including crystallographic texture. Consideration will also be given to the on–line measurement of microstructure and properties with implication for on–line control during manufacture. It will be shown that a combined approach using physical, as well as numerical, models, allows for the successful development of new products and the supporting scientific discipline.