Aluminium has been used as a lightweight alternative to steel throughout the automotive and aerospace industries for many years but is held back by its higher market price. Although aluminium has lower strength than advanced steels, it is a lighter alternative with many improved performance characteristics over the more common metals and alloys.
Automotive manufacturers such as Jaguar have sought to replace steel entirely with aluminium, but so far the lightweighting advantages have come at a price premium keeping this application the domain of luxury vehicle makers. Tactical application of aluminium for specific parts is common across the industry. In Aerospace however, aluminium is the primary airframe material, comprising about 80 per cent of an aircraft’s unladen weight. The sustainability credentials of aluminuim are strong too:
- The aluminium drink can is the world’s most recycled container – more than 65% of all cans are recycled worldwide
- Approximately 75% of all the aluminium ever produced is still in productive use
- Recycling of aluminium products needs only 5% of the energy needed for primary aluminium production.
- Considerably lighter than steel alternatives
- Higher structural stiffness
- Aluminium can be recycled indefinitely without loss in quality
- High cost of material
- High initial cost of transitioning from steels to aluminium
- Primary aluminium production consumes a considerable amount of energy
Magnesium is one of the lightest structural metals available and weighs about 25% as much as steel. It is particularly useful for castings and has the best strength to weight ratio of all the standard structural metals. However, like aluminium, magnesium suffers from a higher cost compared to steels and a volatile price market makes using the material in the long term difficult.
Use of magnesium as an alternative to steels began in the aerospace industry where pressures for producing lighter components have existed for many years. With automotive manufacturers now facing similar challenges, magnesium has increased in application and covers components such as wheels, mount brackets, instrument panels, intake manifolds, cylinder head covers, steering components, IP beams and seat frames.
Use as a structural metal in magnesium alloys represents about a third of the industrial application of this material. Alloying with aluminum represents 40-45% of the industrial usage while application to desulfurization for iron and steel processing consumes 13%.
Advantages of Magnesium
- Considerably lighter than steels
- Best strength-to-weight ratio of commonly used structural metals
- Excellent damping capacity
Disadvantages of Magnesium
- Concerns about general corrosion performance
- A volatile market can affect price considerably
- High melting point can make magnesium components difficult to weld with adhesives often used as an alternative
Titanium is another metal prized for its high strength to weight ratio as well as being highly corrosion resistant. In fact, titanium is reported to have the highest strength to weight ration of any metal. The material is 45% lighter than steel while retaining the same levels of strength and similar in weight to aluminum but more than twice as strong.
The inherent properties of Titanium can be further enhanced by creating an alloy with iron, aluminium and other elements to produce very strong and lightweight materials.
Many industries take advantage of titanium’s high strength to weight ratios, often using it as an alloy. In the aerospace market, titanium is used for jet engine discs, blades, shafts and casings as well as a wide variety of airframe applications including fasteners, landing gear and wing beams. To illustrate its use, titanium makes up around 15% of the Boeing 787 aircraft. The military industry often utilizes titanium for lightweight armour plating while the marine industry take advantage of the materials corrosion resistance to manufacturer high quality propellers.
Advantages of Titanium
- Highest strength to weight ration of any metal
- High corrosion resistance
- High fatigue resistance
Disadvantages of Titanium
- Material stiffness not as good as aluminum alloys or carbon fiber
- Comparatively high cost