As a consequence of the fiercely competitive nature of this new century and because we face an increase in environmental protection requirements, car manufacturers have begun developing materials as alternatives to steel and iron. While efficiency and costs are prioritised in production, vehicles that consume less fuel, and which have higher and simpler recycling combined with driving safety and comfort are produced. For these reasons, aluminium alloys have become an indispensable material for the automotive industry.
Features that lead to aluminium being the most preferred material are:
- It is the second most widely available metal on earth
- It is highly recyclable; it can be re-melted using only 5% of the energy required for production from its raw state
- Aluminium alloys can be worked at high temperatures
- Its use in the production of low weight/high strength products: aluminium is three times lighter than iron
- It can be produced to a thickness of thin wall panels.
- Resistant to corrosion
- High thermal and electrical conductivity
- Easy to shape and format
- It is environmentally friendly: replacing every kilogram of steel with 500g of aluminium will result in ten kilograms fewer emissions over the life of the vehicle.
High-strength alloys can be formed by adding elements such as copper, silicon, zinc, magnesium, manganese, etc. to pure aluminium, which is soft and low in strength.
The classification according to alloying elements in EN standards is as follows
| Alloying | Feature | Areas of use |
| 1XXX | Pure aluminium | Drawn tubes (pipes), chemical equipment, foil, electrical conductors, aircraft parts |
| 2XXX | Aluminium-copper alloys | Aircraft parts, aluminium coated sheets, cryogenic equipment, space shuttle, various tanks |
| 3XXX | Aluminium-manganese alloys | Sheets, rigid sheets, decorative products, beverage cans |
| 4XXX | Aluminium-silicon alloys | Automotive, white goods, lighting, architectural products |
| 5XXX | Aluminium-magnesium alloys | Automotive, marine, cryogenic products, aircraft |
| 6XXX | Aluminium-magnesium-silicon alloys | Automotive products, products manufactured by heat treatment and extrusion technology |
| 7XXX | Aluminium-zinc-magnesium alloys | Moulds, aircraft parts, parts where great toughness is required |
| 8XXX | Lithium, iron, etc. alloys from elements | Products which need to withstand high temperatures, electrical cables |
Al-Si, Al-Mg, Al-Cu, Al-Zn alloys are widely preferred, although different alloys are prepared according to place of use and product requirements.
Material density, desired mechanical properties, melting temperatures are important factors in selecting the alloy to suit your design needs.
Aluminium Silicon Alloys
Al-Si Alloys: This type is the most commonly used aluminium alloy. When the ratio of silicon in aluminium alloys approaches 11.7%:
- The fluidity of the liquid metal therefore its castability increases
- Solidification resistance is reduced
- Increases sealing under pressure
- Reduced tendency to crack or tear during solidification
- Hardness increases
- The specific weight decreases
- Thermal expansion is reduced
- Resistance to corrosion is improved
Al-Si alloys are used in the production of welded structures, sheet production, cylinder heads, engine blocks and valve bodies.
Aluminium Manganese Alloys
Al-Mg Alloys : Manganese is the element that contributes to co-proportional deformation in aluminium alloys.
In aluminium alloys, when manganese rises above 0.5%, it significantly increases yield and tensile strength without reducing ductility
The addition of manganese also improves corrosion resistance and welding outcomes.
Magnesium is light in weight and has a durable structure for certain cast parts. The use of magnesium components instead of heavier aluminium components can contribute to lower fuel costs in vehicles and car manufacturers are developing new technologies to exploit the unique properties of magnesium.
But magnesium is difficult to cast because it is used at high temperatures and oxidizes quickly. It is selected for structural products, boilers and tanks, land and rail vehicles.
Aluminium Copper Alloys
Al-Cu Alloys: Copper is the oldest element used as an alloying element for aluminium.
Copper content in the range of 2 % – 3 % increases tensile strength and hardness at high temperatures and improves mechanical properties
Copper also improves the machinability of alloys.
But copper has a negative effect on aluminium’s ductility and corrosion resistance. During solidification its sensitivity to cracking is high.
Al-Cu alloys are especially chosen for where high strength and heat treatment is needed particularly in high-tensile parts, aircraft structural elements, fringe forged parts, heavy-duty vehicle wheels, cylinder heads and pistons.
Aluminium Zinc Magnesium Alloys
Al-Zn Alloys: Zinc-aluminium alloys are favoured for casting parts with narrow tolerance and thin walled cross-section parts. Like magnesium and aluminium, zinc has good corrosion resistance and dimensional stability, high strength and electrical conductivity. Zinc alloys are generally referred to as ZAMAK in the market.