Aluminum alloys are a mixture of aluminum and a variety of other metals. Different metals, when added to the base aluminum impart enhanced properties to the aluminum, such as enhanced corrosion resistance, better formability, greater strength, and/or other beneficial properties, in a wide range of permutations and combinations.
The alloying elements include silicone, manganese, magnesium, copper, zinc, nickel chromium, and titanium. In a few instances, one can find the use of lead, bismuth, vanadium, chromium, zirconium, iron, and/or boron. Each will change not only the various properties of the aluminum compound, but its density, as well.
The 1000 Series of alloys:
The 1000 series of alloys are generally considered “soft alloys”. They are probably most commonly used in electrical and chemical applications, but can be found in tube, pipe, extrusions, rod, wire, foil, and other applications.
They contain a minimum of 99% aluminum, and usually only a trace of any other metals, with one of the few exceptions being 1100, which contains 0.12% copper. Otherwise, the main impurities are iron and silicone.
Because of the high aluminum content, they have low mechanical properties, giving them good workability. They have very good corrosion resistance and both thermal and electrical conductivity.
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The 2000 Series of alloys:
The 2000 series of alloys are a set of “hard alloys”. They are probably most commonly used in aircraft and military types of applications. Other 2000 series uses include sheet and plate, armor plate, wire, rod, bar, extrusions, tube, and forgings.
Copper is the primary alloying element of this group, but many contain noticeable quantities of silicone, manganese, magnesium, nickel, and/or titanium.
They tend towards high strength, but require solution heat treating to achieve their maximum properties and/or artificial aging. After heat treating, they may approach the properties of mild steel. Good machinability is a benefit offered in this series, but it doesn’t offer the best of corrosion resistance. 2024 is probably the widest used and best known aircraft alloy.
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The 3000 Series of alloys:
The 3000 series of alloys are another set of “soft alloys”. Manganese is the primary alloying element. Copper and magnesium are also often included. 3003 offers fairly good strengths and good workability, and the series is generally fairly corrosion resistant, though generally not favored for its machinability. Their uses include sheet, plate, and tube and pipe.
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The 4000 Series of alloys:
The 4000 series of alloys contain quite high silicon contents, and are typically not used for extrusion purposes. They are popular for a variety of welding wire and brazing wire applications. Their uses include sheet, forgings and welding and brazing products.
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The 5000 Series of alloys:
The 5000 series of alloys are another set of “hard alloys”. They contain comparatively high percentages of magnesium, and have manganese, chromium and titanium as their other primary alloying elements.
They offer very good marine corrosion resistance, making them popular for maritime applications. Their uses include sheet, plate, wire, tubes, conductors, forging stock, armor, welding rods and electrodes and foil.
5000 series alloys have low to moderate strength, but, like the 4000 series alloys, have good welding characteristics. They are not very friendly to cold working applications, and elevated temperatures can lead to stress corrosion.
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The 6000 Series of alloys:
In the USA , the 6000 series features magnesium and silicone as its primary alloying elements, with all of the other common alloy metals being used in one or more of the series.
They account for the vast majority of the tonnage of aluminum extrusions produced. Many of these alloys are comparatively cheap, readily available, and durable. They finish well, and are the “work horses” of the extruded products industry. They offer good corrosion resistance, machinability, weldability, formability, and at least medium strength. They are also heat treatable. They can be solution heat treated and artificially aged. Up to a T-6 temper.
Some of the more common 6000 series alloys are discussed below in a narrative sequence for easy and logical reading, rather than in series number order.
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The 7000 Series Of Alloys:
The 7000 series of alloys contain comparatively high percentages of zinc as their primary alloying element. Silicon, nickel, manganese are not commonly found in them.
They offer high strength, good machinability and are heat treatable, but have poor corrosion resistance. They are another set of “hard alloys”. They are also probably most commonly used in aircraft and military applications. They are found in sheet and plate, wire, rod, bar, extrusions, structural shapes, tubing, forgings, etc.
7075 is among the highest strength aluminum alloys available, and is, especially, often used in aircraft structural applications.
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