All about aluminium


All types of vehicles, from bikes to spaceships, are made from aluminium. This metal allows people to move at breakneck speeds, cross oceans, fly in the sky and even leave our planet. Transport also accounts for the largest share of aluminium consumption: 27%. This figure is bound to keep growing over the next few years.

«The speed was power, the speed was joy, and the speed was pure beauty.»

Richard Bach
Jonathan Livingstone Seagull
Aerospace and aviation
Aluminium will always be thought of as the metal that allowed people to fly. Light, strong and flexible, it proved an ideal material for building heavier-than-air aircraft. There's a reason that in some circles aluminium is known as the 'winged metal'.

Aluminium makes up 75-80% of a modern aircraft and it was actually first used in aviation before aeroplanes were invented. Thus Count Ferdinand Zeppelin made the frames of his famous airships from aluminium.

The breakthrough that laid the foundation for modern aviation occurred in 1903 when the Wright brothers flew their Flyer-1, the first heavier-than-air steerable aircraft. Automobile engines back then weighed too much and didn't deliver enough power to let an aircraft take to the air. So, a special engine was built for the Flier-1 aircraft that incorporated parts, such as the cylinder block, that had been cast from aluminium.
Later aluminium gradually replaced wood, steel and other materials in the bodies of the first aircraft and by 1917 the famous German aircraft designer Hugo Junkers built the world's first full metal aircraft whose fuselage had been made from duralumin, an aluminium alloy that also includes copper (4.5%), magnesium (1.5%) and manganese (0.5%). The unique alloy was developed in 1909 by Alfred Wilm, who also discovered that this alloy can be 'distressed', i.e. it gets significantly stronger after being heat-treated for an extended period.

During the first world war duralumin was a genuine military technology. Its composition and heat treatment methods were classified because it was a strategic material for aircraft manufacturing.

Since then aluminium has become a key manufacturing material in aviation. The composition of aluminium alloys used in aircraft has changed, aeroplanes have gotten better, but the main goal of aircraft designers remains the same: build a plane that is as light as possible with the maximum possible capacity that uses the least possible amount of fuel and whose body doesn't rust over time. It's aluminium that allows aviation engineers to hit all these targets. In modern aircraft aluminium is used literally everywhere: in the fuselage, in the trims, in wing panes and in the rudder, in the tie down systems in the exhaust pipes, in the feeding blocks, in the refuelling hoses, in the door and floors, in the frames of pilot and passenger seats, in the fuel nozzles, in the hydraulic systems, in the cabin pillars, in ball bearings, in the instrumentation in the cockpit, in the engine turbines and in lots of other places.

The key aluminium alloys used in aviation are the 2ххх, 3ххх, 5ххх, 6ххх and 7ххх series. The 2xxx series is recommended for use in high temperature environments and in environments with an increased yield coefficient. The 7xxx alloys are used for lower temperature environments in parts exposed to increased loads and in parts that need to deliver high corrosion resistance under high voltage. 3xxx, 5xxx and 6xxx alloys are used in low load parts, as well as in hydraulic, lubrication and fuel systems.

The most widely used alloy is 7075. It consists of aluminium, zinc, magnesium and copper. It's the strongest of all aluminium alloys and comparable in that respect with steel, however it weighs only a third of what steel weighs.

Aircraft are assembled from sheets and extrusions that are held together by rivets. The number of rivets in a single aircraft can reach millions. Some models use pressed panels instead of sheets and if a crack appears it can only reach the boundary of such a panel. For instance, the wing of the world's largest cargo plane An-124-100 Ruslan, which can carry up to 120 tonnes of cargo, consists of eight pressed aluminium panels each 9 metres wide. The wing is designed in such a way that it will continue to perform its functions even if the panels get damaged.

Today aircraft designers are looking for new materials that offer all the benefits of aluminium but are even lighter. The only candidate they have is carbon fibre. It consists of threads between 5 and 15 um in diameter comprising mostly carbon atoms. The first airliner with a fuselage made completely of composite materials was the Boeing 787 Dreamliner, which made its maiden commercial flight in 2011.

However, aeroplanes made from composite materials cost a lot more to produce than planes made from aluminium. In addition, carbon composite materials often don't deliver the required level of safety.
The key benefit of aluminium alloys used in spacecraft is their ability to withstand high and low temperatures, vibration loads and radiation. In addition, they have the property of cryogenic strengthening, which means that as the temperature falls their strength and flexibility only increase. The alloys most often used in aerospace comprise combinations of aluminium and titanium, aluminium and nickel as well as aluminium, chromium and iron.
Aluminium has proved indispensable not just in aviation but also in the aerospace industry where its combination of low weight and maximum strength is even more critical. The body of the first human-built satellite launched in the USSR in 1957 was made from an aluminium alloy.

All modern spacecraft contain between 50% and 90% of aluminium alloys in their parts. Aluminium alloys are used in the body of Space Shuttle vehicles, they're found in the telescopic antenna of the Hubble space telescope; hydrogen tanks used in rockets are made from aluminium alloys, the tips of rockets use aluminium alloys, parts of launch vehicles and orbital stations, as well as the fastening units for solar panels – all these elements are made from aluminium alloys.

Even solid fuel rocket boosters are made with aluminium. These boosters are used in the first stage of spaceflight and consist of an aluminium powder, an oxidiser such as ammonium perchlorate and a binder. For example, the world's most powerful launch vehicle Saturn-5 (which can take 140 tonnes of cargo into orbit) burns through 36 tonnes of aluminium powder in the time it takes to reach orbit.
Automotive industry
The car is the most common type of transport in the world. The main building material used in cars is the relatively cheap steel. However, as the automotive industry begins to pay more and more attention to fuel efficiency, reducing CO2 emissions and design, aluminium is playing an ever more important role in modern cars.

In 2014 the global automotive industry (excluding China) consumed 2.87 million tonnes of aluminium. By 2020 it's expected to be consuming 4.49 million tonnes of aluminium a year. Key factors of this growth include both rising automotive production and wider use of aluminium in modern cars.

Every kilogram of aluminium used in a car reduces the overall weight of the vehicle by one kilogram. For this reason more and more car parts are being made from aluminium: engine radiators, wheels, bumpers, suspension parts, engine cylinder blocks, transmission bodies and body parts: the hoods, the doors and even the frame. As a result since the 1970s the share of aluminium in the overall weight of an average car has been constantly on the increase: from 35 kg in the 1970s to today's 152 kg. Experts project that by 2025 average aluminium content in a car will reach 250 kg.

Formula 1
Under the new 2015 requirements a Formula 1 race car must weigh at least 702 kilograms. Two thirds of this weight is aluminium. While the outer surface of the body is made from fibre plastic all the internal components and parts are made from aluminium alloys
Aluminium's been used in the automotive industry practically from day one of the mass production of aluminium. In 1899 the first full aluminium body car, the Durkopp sports car, was showcased at an international exhibition in Berlin. And in 1901 the first aluminium engine made its debut at a race in Nice: it had been built by the famous German inventor Karl Benz. In 1962 legendary racer Mickey Thompson drove a car powered by an aluminium engine in the Indianapolis 500 race and finished in record time. A lot of companies later improved on this basic aluminium engine design and used it in various mass produced and racing models, including in Formula-1 race cars. Interest in aluminium parts surged after the oil crisis of the 1970s. Obsessed with fuel economy, car designers started replacing heavy steel parts with lighter aluminium substitutes to reduce the overall weight of their vehicles.

Mickey Thompson
Indianapolis 500, 1962
Range Rover
The latest all-aluminium vehicle from Range Rover is 39% or 420 kilograms lighter than its steel predecessor. This is equivalent to the weight of five people.
Aluminium was first used in car bodies in the premium segment. Thus, the first mass produced car with a full aluminium body was the Audi A8, which made its debut in 1994. Other luxury brands soon followed suit: BMW, Mercedes-Benz, Porsche, Land Rover, Jaguar.

2014 saw another milestone in the automotive industry, an all-aluminium body vehicle was released in the mass market segment: it was the latest iteration of the iconic Ford-150 truck, the US's most popular pickup in the past 38 years. By switching to an all-aluminium design, the vehicle was made 315 kg lighter than the preceding model, allowing it to boast much better fuel economy and significantly lower CO2 emissions. The cargo carrying capacity was also increased, and the model has better acceleration and braking characteristics. At the same time, the truck's been given the highest reliability rating by NHTSA, five stars instead of the four stars that the previous model was given.
The main method for making various auto parts is casting and stamping with milled sheets and bands used as the raw materials. However, some parts are made using the unusual method of hard pressing fine aluminium powder (sintered aluminium powder or SAP). Oxidised aluminium powder is placed inside an aluminium container and heated up to a temperature just below the metal's melting point and thus pressure is applied. Parts made in this manner have better than average strength and are used in environments with high temperature and low traction, for instances aluminium engine pistons are made in this manner.

Tesla's additional protection comprises three levels. Level one is an aluminium beam that has a special shape to toss away any object the car bumps into on the road and/or absorb the shock. Level two is a titanium plate that protects the most vulnerable components in the front of the vehicle, and level three is a stamped aluminium shield that dissipates the energy of the shock and lifts the car over solid immobile obstacles.
Aluminium has another very useful property: it's very good at absorbing shock: in fact it's twice as effective at it as steel. For this reason, automakers have long been using aluminium in bumpers. The bottom of the revolutionary Tesla electric car is covered by 8-mm bullet proof aluminium alloy sheets that protect the battery compartment and guarantee safety at speeds of up to 200 kph. Recently the company started installing new aluminium-titanium armour plates on its vehicles that allow them to literally crush concrete and forged steel obstacles that get in the way while allowing the driver to remain in total control of the vehicle.

Another reason why an aluminium body is superior to a steel one in terms of safety is because when aluminium parts get bent or deformed, the deformation remains localised to the areas of impact while the rest of the body retains the original shape, ensuring safety for the passenger compartment.

Experts claim that in the next ten years automakers are going to significantly expand the use of aluminium in their models. Lots and lots of aluminium is going to find its way into body parts and entire car bodies are going to be built from aluminium.

At the same time many automakers are currently negotiating with aluminium producers to build closed-loop production facilities where new aluminium car parts are made from recycled aluminium parts taken out of discarded vehicles. It's hard to imagine a more environmentally friendly production model.
Rail Transport
The use of aluminium in rail transport began almost immediately after the emergence of mass production of aluminium. In 1894 New York, New Haven, and Hartford Railroad, a company that was then owned by banker John Pierpont Morgan, began producing special super light passenger cars with aluminium seats.

However, initially there was more demand for aluminium in the cargo transport segment, where ideally you want to keep the weight of the rolling stock to a minimum in order to maximise the amount of cargo that can be carried.
The first all-aluminium freight cars were made in the US in 1931. They were hopper cars intended for transporting bulk and granulated cargo with funnel-shaped bodies and unloading hatches in the bottom. Today, hopper cars are produced primarily from 6xxx series alloys that have improved strength and better than average corrosion resistance properties.

The first high speed rail system was put into operation in Japan in 1964. The service ran between Tokyo and Osaka and covered the distance of 515 km in 3 hours 10 minutes, reaching speeds of 210 kph. Shinkansen solved a serious transport problem in a region that is home to more than 45 million people.
Today aluminium freight cars are used to transport coal, various rocks and minerals as well as grain, while tanker cars made from aluminium carry acids. There are also special cars for transporting finished goods such as new cars from production facilities to dealerships.

An aluminium freight car is a third lighter than a steel car. Its higher initial costs are recouped in the first two years of operation because it can carry more cargo. At the same time, unlike steel aluminium does not succumb to corrosion, so aluminium freight cars have longer service lives and over 40 years of operation lose only 10% of their value on average.

In passenger cars aluminium allows manufacturers to shave off a third of the weight compared to steel cars. In rapid transit and suburban rail systems where trains have to make a lot of stops, significant savings can be achieved as less energy is needed for acceleration and braking with aluminium cars. In addition, aluminium cars are easier to produce and contain significantly fewer parts.

In long distance rail systems aluminium is widely used in high speed rail systems, which began to be introduced en masse in the 1980s. High speed trains travel at speeds of 360 kph and more. New high speed rail technologies promise speeds in excess of 600 kph.
This is the maglev line that connects Shunghai with Pudun airport in China. The maglev train travels at 450 kph and covers the distance of 30.5 km in just 8 minute.
Aluminium makes it possible to reduce the weight of such trains, which reduces the bends in the rails that add to the friction resistance. In addition, a high speed train, like a plane, has to have an aerodynamic shape and have a minimal amount of protruding parts, and here too aluminium helps the designers out.

High speed trains made from aluminium are used by France's TGV high speed rail systems. Trains for this network began to be developed in the 1970s by Alstom (France) and the first line connecting Paris and Lyon was opened in 1981. Today TGV is Europe's largest high speed rail system and is planned to be used as the basis for a Europe-wide high speed rail system. The first TGV trains were made from steel, but aluminium replaced steel in later generations. Thus the latest model train called AGV is made entirely from aluminium alloys and travels at speeds of up to 360 kph. Today AGV trains are only operated by Italy's Nuovo Transporto Viaggiatori rail system.

The body of Russia's first high speed train Sapsan is also made from aluminium alloys.

The magnetic levitation technology is the next step in the development of high speed rail. Maglev trains are suspended over the tracks on a dense magnetic field, so there is no friction resistance from the track. This means maglevs can achieve unprecedented speeds. During a trial in Japan a speed of 603 kph was achieved.
Ship Building
Modern seafaring vessels are increasingly being built from so-called marine aluminium, an umbrella term that refers to a broad range of aluminium-magnesium alloys (magnesium content varies between 3 and 6%) used in mechanical engineering. These alloys have outstanding corrosion resistance in both fresh- and seawater.

Important properties of marine aluminium include strength and ease of welding. Aluminium sheets and slabs for ship building are made using cold or hot rolling while extrusions, rods and pipes can be made using rolling, pulling or pressing.
The first partially aluminium cutter Le Migron was built in Switzerland in 1891. Several years later a 58-metre torpedo boat was built from aluminium in Scotland. It was very sturdy and achieved a speed of 32 knots, which was unheard of at the time. The boat was called the Hawk and was built for the Russian navy.

Duralumin or magnalium are also used for building high-speed hydrofoil passenger boats that travel at speeds in excess of 80 kph. To ensure high speed and manoeuvrability, these boats need to be very light, thus aluminium comes to the rescue again.


Corrosion in the first
years of operation.


Corrosion in the first
years of operation.
Marine aluminium is 100 times less prone to corrosion than steel. In the first year of operation steel gets covered in corrosion at a rate of 120 mm per year, while aluminium at a rate of only 1 mm per year. In addition, marine aluminium has outstanding strength. It's flexible, and even a powerful blow can't punch a hole in the body of a welded-aluminium boat. Aluminium frames improve seaworthiness, deliver better security and reduce maintenance costs.

It is for this reason that aluminium is used in yachts, motor boats, cutters as well as underwater craft. As a rule, sporting boats are built from aluminium from keel to mast, which gives them a speed advantage, while high capacity vessels are built from steel while the superstructure and other auxiliary equipment is made from aluminium to save weight and increase the cargo carrying capacity.

Photo: © Shutterstock and © Rusal.

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