Chapter 7: Extrusion of Hard Alloys

This chapter discusses the extrusion characteristics of hard aluminum alloys, particularly those in the 5000 and 7000 series. It begins with a review of two studies, one showing how the extrudability of 7xxx alloys varies with the presence and amount of different alloying elements, the other relating minimum wall thickness with circumscribing circle diameter. It then explains how oxides on either the billet or container complicate the control of extrusion as well as auxiliary processes and how material flow and the movement of trapped gasses in different regions of the extrusion can lead to defects and variations in strength. It also discusses the extrusion of aluminum matrix composites and explains how composite billets are made.