Development of directional microstructures in mechanical processing of aluminium alloys

The principal processes (rolling, extrusion, and forging) for the commercial production of wrought aluminium alloys are briefly described and their effects on mechanical deformation patterns reviewed with special reference to the type of alloy and its initial, intermediate, and final metallurgical structure. The effects of thermal treatments, both during and after the mechanical working sequences, are described and the metallurgical interactions caused by them reviewed in terms of the modifications of directional structures produced. Modifications to directional structures which can lead to favourable or unfavourable effects on the properties of the main groups of commercial wrought alloys are described and methods of controlling these effects by adjusting alloy composition, as well as mechanical and thermal treatment sequences, are discussed. It is concluded that the directional structures produced in wrought aluminium alloys are influenced not only by the working process and the product geometry, but also by the metallurgical features of the material. In particular, the transitional elements (Mn, Cr, Zr) added to many aluminium alloys can exert a strong influence on directional microstructures, especially in hot-worked material.