Which aluminum alloys Are Already Maturely Used in Automobile Manufacturing?

After years of technological iteration, 5xxx aluminum alloys has evolved from an initial niche application to a standard material in mid-to-high-end vehicles, particularly in three major areas: body panels, chassis components, and fuel/electric system components, where its application is most mature.

1. Body Panels

Body panels are the most widely used area for 5 Series aluminum alloy, including the hood, door shells, roof, fenders, and trunk lid. Taking the BMW 5 Series as an example, its steel-aluminum hybrid body structure utilizes 5 Series aluminum alloy (such as models 5754 and 5182 aluminum alloy) in these key body panels, achieving a weight reduction of over 30%.

2. Chassis Components

As the "skeleton" of a vehicle, the chassis demands extremely high strength and fatigue resistance from its materials. 5 Series aluminum alloy, with its excellent overall performance, has secured a place in key chassis components.

Due to its high corrosion resistance, 5083 aluminum alloy is also used in chassis protection components such as underbody protection plates and air tanks, effectively resisting the impact of road debris and rainwater erosion, thus extending the service life of the chassis. This type of application has been validated by the market over a long period, demonstrating high technological maturity and becoming a standard solution for automakers to improve chassis performance.

3. Fuel and Electric System Components

In the field of gasoline vehicles, 5052 5-series aluminum alloy, due to its combination of strength and formability, is an ideal material for automotive fuel tanks and fuel lines. Aluminum alloy fuel tanks formed through cold stamping are lighter than traditional steel fuel tanks and have excellent vibration fatigue resistance, better adapting to the bumpy conditions encountered during vehicle operation.

With the development of new energy vehicles, the application of 5-series aluminum alloy in the electric system is also becoming increasingly mature. Among them, the 5652 model, due to its high purity and chemical corrosion resistance, is used to manufacture battery casings. It resists electrolyte corrosion and possesses excellent heat dissipation performance, ensuring battery safety. The 5083 model is used for new energy battery trays, further reducing overall vehicle weight and increasing driving range while meeting structural strength requirements.

The Stringent Requirements for 5-Series Aluminum Alloys in Automobiles

To serve in critical automotive components, 5-series aluminum alloys must meet multi-dimensional performance requirements, covering mechanical properties, processing performance, corrosion resistance, and other aspects. Some indicators even reach high industry standards.

1. Precise Mechanical Performance Indicators

Different application scenarios have different requirements for mechanical properties, but core indicators include tensile strength, elongation, and yield strength. Taking 5-series aluminum alloy (5754 aluminum) for automotive brake discs as an example, its tensile strength needs to reach 210-225 MPa, the specified non-proportional elongation strength 100-120 MPa, and the elongation after fracture 22-25%. It also needs to pass 90° and 180° 0t bending tests to ensure a smooth, crack-free surface after bending.

For 5-series aluminum alloys used in body panels, the requirements place greater emphasis on formability. They typically need a lower yield strength ratio and a higher formability limit. For example, the yield strength in the T4(p) state needs to be between 90-140 MPa, and the elongation should not be less than 20%, to accommodate the stamping requirements of complex curved surfaces. 5-series aluminum alloys used in chassis components have even higher requirements for fatigue strength, needing to withstand long-term bumps and load impacts to ensure driving safety.

2. Excellent Machining and Welding Performance

Automotive parts manufacturing involves multiple processes such as stamping, welding, and bending, which requires 5-series aluminum alloys to have excellent machinability. In the stamping process, the lug rate must be strictly controlled (ideally within the range of 1.1–2.0%) to avoid reduced product utilization or cracking due to uneven material deformation.

Simultaneously, the problem of Lüders bands (surface stripe defects) that easily occur during stamping needs to be addressed, especially for vehicles using a no-primer coating process. Surface defects directly affect the appearance quality; therefore, this defect needs to be eliminated by optimizing the chemical composition and processing technology (such as adjusting the cold rolling deformation rate and the finished product annealing temperature).

Weldability is also a key requirement. The assembly of car bodies and chassis requires numerous welding processes. 5-series aluminum alloys must ensure that the joint strength does not decrease after welding, and that the corrosion resistance of the weld is stable. Furthermore, for complex curved surface components (such as door inner panels), the material must also possess good stamping formability, adapting to complex processing procedures such as deep drawing and multi-pass bending.

3. Stringent Corrosion Resistance and Environmental Adaptability

The automotive driving environment is complex, requiring the vehicle to withstand the corrosive effects of rain, snow, and road salt. Therefore, 5-series aluminum alloys must possess excellent corrosion resistance. In its natural state, aluminum alloys form an oxide film on their surface to prevent corrosion. However, 5-series aluminum alloys used in automobiles still require special treatment to enhance their protective capabilities, especially for components such as the chassis and fuel tank that come into direct contact with corrosive media.

Simultaneously, the material must meet environmental protection requirements. Traditional aluminum alloy processing uses alkaline cleaning processes, which are not in line with green production trends. Therefore, the next generation of automotive 5-series aluminum alloys needs optimized manufacturing processes to avoid the use of harmful chemical reagents and reduce energy consumption during production.

Furthermore, the material's performance must remain stable under high and low temperature environments. For example, in the high-temperature environment of the engine compartment, it must possess good high-temperature resistance; when driving in low-temperature areas, it must avoid performance degradation due to low-temperature embrittlement.

4. Stable Chemical Composition Control

The performance of 5-series aluminum alloys largely depends on the chemical composition ratio; therefore, the content of each element must be strictly controlled. Taking automotive 5-series aluminum alloy as an example, the typical component ratio (by mass percentage) is: Si≤0.1%, Fe≤0.2%, Cu≤0.05%, Mn:0.15～0.25%, Mg:2.9～3.05%, Zn≤0.05%, and total impurities≤0.15%.

Among these, the precise control of magnesium content is particularly critical, directly affecting the material's strength and formability; excessive impurity content will reduce the material's corrosion resistance and processing performance, therefore, strict control is required during the smelting and refining processes.