Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. Aluminium has excellent resistance to corrosion due to the thin layer of aluminium oxide that forms on the surface of material when exposed to air.
Aluminium can be easily fabricated into various forms such as foil, sheet, plate, rod, tube and wire.
Application for Aluminium:
- Cooking Utensil
- Heat Exchange
- Electrical Conductor
Aluminium Alloy Series
I. Wrought Alloys
a) 1XXX – Aluminium of 99% Minimum Purity
This aluminium is used for applications where the support of significant loads is not required, but for applications where a extremely good corrosion resistance is required, where an impermeable barrier is required, or where electrical conductance is prime consideration.
Depending on the requirements different purity levels of this grade of aluminium are available, where ‘1100’ has a minimum 99% aluminium and is used for food and pharmaceutical packaging, and ‘1350’ is used for electrical conducting applications, where a tight restriction is placed on the elements that are not aluminium, to optimize the electrical conducting properties.
This aluminium grade is non-heat treatable, but can be strain hardened. The low strength properties of this grade allows for the material to be shaped easily.
b) 2XXX – Aluminium & Copper Alloys
This aluminium grade is heat treatable and provides high strength alloys that perform well over a wide temperature range. The strength to weight ratio of the alloy ‘2024’ promotes its use on aerospace applications that are bolted or riveted together. For welded structures, the alloys ‘2219’ and ‘2048’ are used, although these need to be painted to provide additional resistance to corrosion. The content of impurities is controlled in alloys similar to ‘2124’ to provide a material structure that is significantly more resistant to shock loads.
c) 3XXX – Aluminium & Manganese Alloys
This alloy group is widely used in applications that require resistance to corrosion and chemical attack, properties that allow it to be formed into complex shapes and the ability to be joined by welding, brazing or soldering. These alloys provide medium strength characteristics that cannot be improved by heat treating, but they can be stain hardened. Applications include sheet metal cladding for the construction industry and beverage cans.
d) 4XXX – Aluminium & Silicon Alloys
The addition of silicon to aluminium in this range of alloys improves the ability of the material to be formed into complex shapes for forging and to provide an excellent gap filling capability when used as filler in the welding of aluminium alloy parts, especially welding of 6XXX series components. These alloys are heat treatable and provide medium to high strength alloys.
e) 5XXX – Aluminium & Magnesium Alloys
These alloys exhibit medium to high strength properties and are strain hardenable. Their ability to provide load support at temperatures as low as absolute zero, and their excellent corrosion resistance finds their use in a wide range of applications in the cryogenic freezer, construction and marine industries. The good weldability and toughness properties of this alloy group are utilized in the previous industries and promote its use in the automotive industries. For components that are exposed to temperatures above 100°C, the content of magnesium must be limited to a maximum of 3% to reduce the potential of stress corrosion cracking problems.
f) 6XXX – Aluminium, Magnesium & Silicon Alloys
As with the 4XXX series, the addition of silicon to the composition provides an ability to be formed into complex shapes. This functionality is used in the manufacture of complex shaped extruded sections to allow the designer to provide strength and/or stiffness in the areas where it is needed to provide a high strength/stiffness to weight ratio component. These alloys are heat treatable, providing medium to high strength properties. They provide very high resistance to corrosion, they can be easily welded ad conduct electricity well. Application of these alloys includes automotive body panels and structures, machine and civil engineering structural members and high strength electrical conductors.
g) 7XXX – Aluminium, Zinc & Magnesium Alloys
These are heat treatable and can provide very high strength and very high toughness aluminium alloys. The toughness levels are achieved by controlling the amount of impurities to provide a refined grain structure. These alloys can be welded, but this requires advanced technology and which is avoided if mechanical fastening can be used. The corrosion resistance of 7XXX alloys is average, so for exposed applications a coating is required. These alloys can be costly and sometimes require advanced tempering methods, so their application is normally limited to high performance applications in aerospace structures.
h) 8XXX – Miscellaneous Aluminium Alloys
This alloys group encompasses aluminium alloys that include elements that are not used in significantly quantities in the other grades, such as Iron, Nickel and Lithium. Iron and Nickel alloys generally increase the strength of aluminium without reducing the electrical conducting properties. Lithium is used to increase the stiffness and strength properties for low component mass requirements.
II. Casting Alloys
a) 1XX.X – Aluminium of 99% Minimum Purity
1XX.X grade aluminium does not produce cast components that are suitable for supporting loads.
b) 2XX.X – Aluminium & Copper Alloys
Used for high strength and high toughness components. Addition of the other elements provides special alloys for high performance in high temperature applications. These alloys are heat treatable.
c) 3XX.X – Aluminium, Silicon and Copper & / or Magnesium Alloys
As with the wrought aluminium alloys, the addition of silicon improves the ability of the material to be formed into complex shapes. These alloys can be cast using a variety of techniques to provide components that exhibit moderate strengths, and some alloys provide good toughness properties. Selection of the alloy depends on the casting technique being used. Some of the alloys in this range can be formulated using recycled aluminium.
d) 4XX.X – Aluminium & Silicon Alloys
These alloys cannot be heat treated and provide medium strength materials. Again the silicon component provides excellent fluidity. The resulting components can be welded and they provide good corrosion resistance.
e) 5XX.X – Aluminium & Magnesium Alloys
These alloys are selected for components that require high levels of corrosion resistance and moderate strength properties. These alloys are not widely used as a result of difficulties experienced in casting. Resulting components can be easily machined and specific alloys can be anodized.
f) 7XX.X – Aluminium & Zinc Alloys
These alloys can be heat treated to provide medium to high strength properties. The resulting components exhibit a superior surface finish and can be machined easily. Application of this alloy group are limited to low specification components, this is a result of complications experienced during casting.
g) 8XX.X – Aluminium & Tin Alloys
Aluminium and tin alloys exhibit similar properties to that of the 7XX.X alloys, except for their lower strength. Again they are difficult to cast, but the higher quality of the finished machined parts makes them suitable for bearing applications.