Metallurgical features affecting the extrusion of aluminium alloys

Abstract

Wrought alloys are divided into seven major classes according to their principal alloy elements. Each class demonstrates a different type of microstructure because of these alloy differences. Typical microstructural features are described in this chapter for each class and show how microstructure progressively develops from the as-cast ingot to the final wrought form (although this is treated in more detail in Chapter 4). Furthermore, alloy classes can be divided into two categories according to whether they are strengthened by work hardening only or by heat treatment (precipitation hardening). The former applies to 1XXX, 3XXX, 4XXX and 5XXX alloys, while the latter applies to 2XXX, 6XXX and 7XXX alloys.We shall also consider some of the more recently developed Al-Li alloys.