Different aluminum alloys extrusion

Extruded structural sections are produced by hot extrusion in which a heated cylindrical billet is pushed under high pressure through a steel die to produce the desired structural shape. The extrusion is then fed onto a run-out table where it is straightened by stretching and cut to length. During extrusion, metal flow occurs most rapidly at the center of the ingot resulting in oxides and surface defects being left in the last 10–15% of the extrusion which is discarded.

In general, the stronger the alloy, the more difficult it is to extrude. One of the advantages of the 6XXX (Al-Si-Mg) alloys is that they exhibit good extrudability. On the other hand, the 2XXX (Al-Cu) and 7XXX (Al-Zn) alloys are referred to as “hard” alloys because they are more difficult to extrude.

Alloy Relative extrusion pressure
1100 1.0
3003 1.2
6061 1.6
2014 1.8
7075 2.3

A profile’s shape factor (the ratio of the perimeter of the profile to its area) is an approximate indicator of its extrudability, i.e. the higher the ratio, the more difficult it is to extrude. The extrusion process itself and heat treatable aluminium alloys make it possible to manufacture complex, thin-walled cross-sections with a strength equal to that of ordinary structural steel. The torsional stiffness can be improved by exploiting the advantages of hollow sections.

Unsymmetric shapes, shapes with sharp corners, profiles with large thickness variations across their cross section, and those that contain fine details are all more difficult to extrude. Generous fillets and rounded corners help to reduce extrusion difficulties.


Data from ASM metals handbook vol. 14