The Properties And Usage Of Aluminium Engineering Essay
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Published: Mon, 5 Dec 2016
Physically, chemically and mechanically aluminium is a metal like steel, iron, zinc, lead or more. Aluminium is one of the world’s most abundant elements. After Silicon and Oxygen, it is the most common element found in the Earth’s crust, which measures approximately 7.3% of the Earth’s mass. Although its abundance, it will only found in other compounds due its reactivity.
The Hall-Heroult Method which was developed in 1886 gave a cheaper alternative method of extracting aluminium. Because of its cheap process, its production has vastly increased. Now, aluminium can be found in many items from ladders, cars, power lines to space and it is this lightweight property along with its strength that can be obtained in certain alloy (by altering the structure), that makes aluminium particularly important in air travel. It’s high level of malleability (2nd most malleable metal) means it can be easily moulded into many shapes. Although aluminium has only 63% the electrical conductivity of copper it weighs just half as much, and given its world’s 6th most ductile metal its ideal for longer distance power cables.
Aluminium forms a 5nm thick protective layer when exposed to air, making the metal very resistive corrosion, and ideal for using in the building industry as it is virtually maintenance free. Although of its many advantages, Aluminium has some weaknesses but these are few.
Aluminium’s various usage in various sector from home appliances to aeronautics is contributed by its own distinctive properties which is beneficial in many different ways.
â€¢ Low density. Aluminium is only one-third the weight of steel due to its low density which is 2.70 g·cmâˆ’3 . This property plays significant role in making items.
â€¢ Aluminium including its alloys, is highly resistive corrosion. The coating of aluminium oxide provides an effective shield to corrosion elements and chemical attack.
â€¢ Aluminium is an excellent conductor of electricity. It can be the alternative of copper by in many electrical applications.
â€¢ Aluminium is non-magnetic material and non-combustible, which plays big role in most advanced industries like electronics or in offshore structures.
â€¢ Aluminium is non-toxic, very useful and established element that has widely used in the food and packaging industries since many decades ago.
â€¢ Aluminium alloy has very strong tensile strength, although pure aluminium has low tensile strength. In space missions, aluminium is vastly used because it’s very high strength and very light weight.
â€¢ High reflectivity. Common mirrors are made by aluminium.
â€¢ Effective heat barrier and excellent heat conductor. Satellites uses aluminium layers to protect its components.
â€¢ Malleable and easily worked by the common manufacturing and shaping processes.
Given with its abundance, aluminium never be found on its pure form in the nature unlike the gold and silver, due to its higher level of reactivity, when it is found, it is bonded to other elements such as the most common one, bauxite (aluminium oxide) that has the formula of Al2O3.2H2O. There are also impurities are present in the Bauxite, which Bayer Process is used to separate the components.
Bauxite reserves are spread across the world. Large deposits include: Australia, Brazil, Guinea and Jamaica. Around 85% of all Bauxite mined from the Earth is used to produce aluminium metal, which goes on to be used for a huge variety of uses. The remaining 15% goes towards chemical and refractory materials, along with making aluminium compounds.
Aluminium has become an essential metal in our everyday lifestyles and luckily the known reserves of Bauxite are thought to be plentiful enough to maintain supplies of aluminium for some centuries to come. A publication by the International Institute for Environment and Development, states that in the year 1999 there were around 25 billion metric tonnes of Bauxite ore, that is just about enough for everyone on the planet to have 4000 kg of Bauxite each, which means approximately 500 kg of Aluminium. They estimate that if the amount of production does not increase, that the supplies could last over 200 years.
As a result of its low density, low cost, and corrosion resistance, Aluminum is widely used around the world. It is used in an extensive range of products from drinks cans to window frames and boats to aircrafts. A Boeing 747-400 contains 147,000 pounds (66,150 kg) of aluminium.
Unlike some metals, aluminum has no aroma, hence its widespread use in food packaging and cooking pots as we can see. Although not quite as good as silver or copper, aluminum can also be considered as an excellent electrical conductor. It is also considerably cheaper and lighter than other metals, so it is used widely in overhead power lines.
Aluminium is used excessively in the modern world, and the uses of the metal are extremely diverse due to its many unusual combinations of properties, that are around 270. No other metallic element can be used in so many ways across such a variety of domains, like in the home, in transport, on land, sea and in air, and in industry and commerce.
One of the most common end uses of aluminium as discussed before is packaging, including drinks cans, foil wrappings, bottle tops and foil containers. Each of these relies on aluminium to provide a way of containing the food cleanly, and to protect it from changes in the local environment outside the packaging. Aluminium is still used in a very big way in the food packaging industry despite recent health worries linking aluminium to Alzheimer’s disease. Aluminium’s natural resistance to corrosion aids it in its role in packaging (and many other areas), as unlike in iron, aluminium oxide forms a protective and not destructive layer. Aluminium is also completely impermeable, (even when rolled into extremely thin foil), and also doesn’t let the aroma or taste out of food packaging, the metal is non-toxic and aroma less itself too, making it perfect for packaging.
Aluminium’s unbeatable strength to weight ratio gives it many uses in the transport industry. Transport is all about moving things around and to do so a force is always required. As according to the Newton’s Second Law of Motion, less force is needed to move a lighter object to certain acceleration than is needed to get a heavier object to the same acceleration. As aluminium is so lightweight this means that less energy needs to be used to move a vehicle made with aluminium than one made from a heavier metal such as steel. For example, a same designed car made with aluminium will have 3 times faster acceleration than made of steel.
All the above properties can be found in an impressive array of commercially available alloys. The composition and logic of those alloys are regulated by an internationally agreed classifications system or nomenclature for wrought alloys and by various domestic nomenclature schemes for the casting alloys. The wrought alloy scheme, as adopted by the British Standards Institution, by CEN and by the other standards organisations globally, is as follows. Each registered alloy is described by a four digit number, with a further letter and number indicating the temper, or condition of the alloy, For example, 6082-T6 is a medium strength grade alloy based on the aluminium-magnesium-silicon family, in the fully heat-treated condition. Alloys fall into two main groups. The work-hardening alloys, such as the 3000 series, where strength is achieved by the amount of “cold work” applied to the alloy, e.g. by rolling, and the heat-treatable or precipitation hardening alloys, such as the 6000 series, where the strength and properties are achieved by heat treatments of varying complexity.
Although aluminium isn’t the strongest of metals, its alloys’ of combination with other elements increase its strength significantly. With trains, boats and cars, aluminium is useful for this lightweight property (which also gives fuel efficiency), in airplanes however maintaining a relatively low weight is vital (in order to level the ground), and aluminium allows planes to have this. In modern planes aluminium makes up to 80% of their weight, and a normal Boeing 747 contains about 75 000 kg of the metal. Its high corrosion resistivity is an advantage in transport (as well as packaging) as it makes painting planes unnecessary saving some hundreds of kilograms of further weight.
Weight is also important in aluminium’s electrical uses, where its low density makes it the first choice for long distance power lines despite having just 63% of the electrical conductivity of copper. In fact 1 kg of aluminium conducts almost twice as much electricity as 1 kg of copper. Since 1945, aluminium has been used in high voltage electrical transmission, in place of copper as it is the most cost efficient power line material. With copper many heavy and expensive support structures needed to be used, yet using aluminium fewer lighter and cheaper supports have to be used. This saves huge amount of money, despite wastage in electricity due to lower conductivity. Aluminium is also more ductile than copper, so it is easier to draw it into wires to produce these power lines. Its corrosion resistance completes aluminium’s profile as the perfect choice for long-distance electricity distribution. Aluminium has other electrical applications too including TV aerials, satellite dishes, and being the standard base for bulbs.
Buildings made with aluminium are virtually maintenance free due to the strength of aluminium’s corrosion resistance. Due to this and its light weight it is used in cladding, windows, skylights, gutters, door frames, and roofing. Insulated aluminium cladding is also very thermally efficient, keeping homes warm in winter, and cool in summer. One layer of insulated aluminium cladding is as effective as four inches of brick or ten of stone.
Aluminium can also be painted and used with other material to achieve a particular effect on the appearance of a building. The metal is extremely versatile and it can be curved, tapered, welded, bonded and cut to any shape to be used for a certain job.
In construction, Aluminium also has further end uses in products used more readily around the home. Like all the other uses they relate specifically back to the properties of the metal. The material is used to make saucepans, kitchen utensils, golf clubs, tennis bats, indoor and outdoor furniture, fridges, toasters, and more.
In a nutshell, Aluminium has a huge number of uses. These range from all sorts of packaging, through to aeroplanes, cars and train carriages. Aluminium is also vital in power lines, the building and construction industry and commonplace household objects. The key features that lend aluminium to these uses are corrosion resistance, low density, ductility, electrical conductivity and strength in alloys.
Although seeing the reserves, it may seem that recycling aluminium is not only unnecessary, but also pointless. This however is not the case. Creating new aluminium from old metal requires just 5% of the energy needed to create the aluminium in the first place. It also releases just 5% of the greenhouse emissions. When one kilogram of aluminium is recycled, 8 kg of Bauxite, 4 kg of chemical products and 14 kilowatt-hours of electricity are saved. Recycled aluminium can be recycled again, and again save all these vast quantities of resources and energy. This in the long-term could do big impact to our nature to save our environment from harms such as greenhouse gases.
Aluminium is a remarkable material, its range of properties make it unique and essential to the modern world. However, like anything, it comes with its drawbacks. Aluminium is not the perfect material.
In 1965 aluminium first became linked with Alzheimer’s disease after injecting rabbits with compounds of the metal caused tangle-like formations of nerves. It was thought that this could lead to the symptoms of dementia shown in sufferers of Alzheimer’s. Although no causal relationship has yet been proved there are still many concerns about the effect of the metal on human health. This is one of the few weaknesses of aluminium, although it is deadly serious and if a definite link were found then an aluminium substitute would have to be found, or all its non-essential uses would have to be stopped.
Aluminium is also thought to cause problems for kidney patients when it enters their body during dialysis, and inhaling aluminium dust is currently linked with some lung problems.
Other than these possible health problems the weaknesses of aluminium are limited. In its pure form it is not very strong, but its alloys can provide any needed strength.
Aluminium is also relatively expensive due to its long and high energy extraction process, hence increasing the cost of manufacturing of products by multiple times than steel.
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