Aluminium, or aluminum as the American’s like to call it, is the third most abundant element comprising about 8% of the Earth’s crust. Despite this fact, it was only discovered in 1807 by Sir Humphrey Davy, who originally called it alumium. Davy identified it in alum, but it was not until 1825 when Oersted produced the first samples of pure aluminium by heating potassium amalgam with anhydrous aluminium chloride.
It was not until the late 1880’s when processes were developed that could produce commercial quantities of aluminium. Most notably the Hall- Héroult process named after Charles Martin Hall and Paul Lois Toussaint Héroult who simultaneously invented the aluminium smelting process in America and France respectively. The Hall- Héroult process was enhanced with the evolution of the Bayer process which produces aluminium oxide, from bauxite, which is used in the Hall- Héroult process.
With commercial smelting now a reality and the price of aluminium dropping, aluminium products could become a reality.
Sources of Aluminium
Bauxite is the most common raw material used to produce virgin aluminium. The five most prolific bauxite-producing nations are Australia, Guinea, Jamaica, Brazil and China. According to 1998 data, Australia produces 2.5 times more bauxite than its nearest rival.
The other source of aluminium is from recycling. With no difference between virgin and recycled aluminium and its alloys, the case for recycling of aluminium is compelling.
Taking 14,000KWH to produce a single tonne of virgin aluminum and just 700KWH to produce a tonne of recycled aluminium, the energy figures alone speak volumes. Combine this with global trends for producing less waste and lower impact on the environment and the case is irrefutable.
In 2003, Europe produced 4 million tones of recycled aluminium. Over one-third of Europe’s aluminium is sourced from recycled materials with sectors such as transport and construction enjoying recycling rates of 90-95%
Properties of Aluminium that Make It So Popular
Aluminium possesses a host of advantageous properties that make it the choice of material for so many applications. These include:
• Lightweight with a density approx 2.7g.cm3 (compared to steel with density typically 7.75-8.05g.cm3)
• High strength to weight ratio
• Excellent corrosion resistance which can be enhanced by anodizing, painting or lacquering
• Excellent conductor of heat and electricity
• Good ductility
• Good reflective properties
Forming and Products
Aluminium is a versatile material that lends itself to many production methods, which in turn means that there are a range of different products that can be made out of aluminium. Common aluminium forming processes include:
• Sand casting
• Die casting
Add to this its ability to be heat treated to tailor properties and its ability to be joined using any number of techniques and aluminium becomes a material with real potential.
Extruded products comprise over half the aluminium products available in europe. The largest consumer of these products is the building industry, which use aluminium extrusions in window and door frames. Other applications for extruded aluminium products include bicycle frames, structural automotive components, pipes and tubes, furniture etc.
Rolled aluminium products consist of plates, sheet and foil, which may vary in thickness from several millimetres think to tens of microns thick.
Sand casting is a versatile technique that is generally used for high-volume production.
Die casting differs from sand casting in that it utilizes re-usable moulds. It can also be carried out at a range of pressures including high pressure die casting, low pressure die casting, gravity die casting, vacuum die casting and squeeze die casting. Of these, high pressure die casting is the most popular accounting for about 50% of all light alloy casting production.
The transport industry consumes nearly a quarter of all aluminium produced. Aluminium is used not only in land-based transport forms such as cars, trucks and trains, but also bicycles, aerospace, ships and boats.
Key properties exploited by the transport industry include light weight leading to reduced fuel consumption, corrosion resistance and recyclability which is becoming increasingly important in view of recent EU directives for the automotive industry.
Aluminium is used for parts such as engine blocks, wheels, brake and suspension components and increasingly for chassis and body panels.
The packaging industry consumes the bulk of the rolled aluminium produced. Rolled aluminium goes into making beverage cans, food containers and foil wrappings, which take advantage of properties such as strength, lightness, impermeability and its odourless nature.
Building and Construction Industry
Extruded, cast and rolled aluminium products are widely used in the building and construction industries. Typical applications include window frames and other glazed structures ranging from shop fronts to large roof superstructures for shopping centres and stadiums; for roofing, siding, and curtain walling, as well as for cast door handles, catches for windows, staircases, heating and air-conditioning systems.
Aluminium has long been used for small boat hulls. Aluminium extrusions are becoming more common place in large ships where designers want to increase the above water line size without adding weight and instability. Hovercrafts, hydrofoils and multi-hulled vessels have also benefited from aluminium usage, where reduced weight translates directly into improved performance.
Aluminium has also become the material of choice for many offshore oil platforms applications where light weight, corrosion resistance and low maintenance are key factors.
Aluminium is a metal and can be processed in a similar manner to other metals such as steel, copper, brass or titanium. However, its properties such as light weight, corrosion resistance and conductivity, combined with sustainability have seen its’ widespread utilization and acceptance.
The future for aluminium remains bright, however, threats from alternative materials such as magnesium should not be ignored, with increasing production and reduced prices opening up areas of possibility.