Aluminiumbronze is a type of bronze in which aluminium is the main alloying metal added to copper, in contrast to standard bronze or brass. A variety of aluminium bronzes of differing compositions have found industrial use, with most ranging from 5% to 11% aluminium by weight, the remaining mass being copper; other alloying agents such as iron, nickel, manganese, and silicon are also sometimes added to aluminium bronzes.
Compositions
The following table lists the most common standard aluminium bronze wrought alloy compositions, by ISO 428 designations. The percentages show the proportional composition of the alloy by weight. Copper is the remainder by weight and is not listed:
Alloy
Aluminium
Iron
Nickel
Manganese
Zinc
Arsenic
CuAl5
4.0–6.5%
0.5% max.
0.8% max.
0.5% max.
0.5% max.
0.4% max.
CuAl8
7.0–9.0%
0.5% max.
0.8% max.
0.5% max.
0.5% max.
CuAl8Fe3
6.5–8.5%
1.5–3.5%
1.0% max.
0.8% max.
0.5% max.
CuAl9Mn2
8.0–10.0%
1.5% max.
0.8% max.
1.5–3.0%
0.5% max.
CuAl10Fe3
8.5–11.0%
2.0–4.0%
1.0% max.
2.0% max.
0.5% max.
CuAl10Fe5Ni5
8.5–11.5%
2.0–6.0%
4.0–6.0%
2.0% max.
0.5% max.
Material properties
Aluminium bronzes are most valued for their higher strength and corrosion resistance as compared to other bronze alloys. These alloys are tarnish-resistant and show low rates of corrosion in atmospheric conditions, low oxidation rates at high temperatures, and low reactivity with sulfurous compounds and other exhaustproducts of combustion. They are also resistant to corrosion in sea water. Aluminium bronzes' resistance to corrosion results from the aluminium in the alloys, which reacts with atmospheric oxygen to form a thin, tough surface layer of alumina which acts as a barrier to corrosion of the copper-rich alloy. The addition of tin can improve corrosion resistance. Another notable property of aluminium bronzes are their biostatic effects. The copper component of the alloy prevents colonization by marine organisms including algae, lichens, barnacles, and mussels, and therefore can be preferable to stainless steel or other non-cupric alloys in applications where such colonization would be unwanted. Aluminium bronzes tend to have a golden color.
Applications
Aluminium bronzes are most commonly used in applications where their resistance to corrosion makes them preferable to other engineering materials. These applications include plain bearings and landing gear components on aircraft, guitar strings, valve components, engine components, underwater fastenings in naval architecture, and ship propellers. Aluminium bronze is also used to fulfil the ATEX directive for Zones 1, 2, 21, and 22. The attractive gold-toned coloration of aluminium bronzes has also led to their use in jewellery. Aluminium bronzes are in the highest demand from the following industries and areas:
