Aluminum Extrusion in Automotive: Safety & EV Revolution

The Automotive Aluminum Extrusion Revolution: Crashworthiness and Electrification

 

As the automotive industry undergoes the most significant transformation in its history, aluminum extrusion technologies are positioned at the center of this shift. The transition from Internal Combustion Engines (ICE) to Electric Vehicles (EV) has completely altered vehicle architecture, elevating the concept of "lightweighting" to the top priority due to range anxiety.

 

In an EV, the battery pack weight can reach up to 700 kg; compensating for this extra mass is only possible through the extensive use of aluminum in chassis and body-in-white (BIW) components.

 

1.1 Crashworthiness and Alloy Science

In modern vehicles, safety is achieved not through "stiffness" but through "controlled deformation." In the event of a crash, chassis components (crash boxes, bumper beams, longitudinal rails) must fold like an accordion to absorb kinetic energy without snapping or cracking. This property is known in metallurgy as "high energy absorption".

 

While traditional 6061 and 6082 alloys offer high strength, they risk brittle behavior during impact. This necessity has triggered the rise of the 6005A alloy.

 

6005A vs. 6061 vs. 6082: Critical Comparison

• 6061 (Al-Mg-Si-Cu): The industry standard for years. Its Copper (Cu) and Chromium (Cr) content increases strength but raises "Quench Sensitivity". This requires the profile to be water-quenched very rapidly after exiting the press; otherwise, mechanical properties degrade. Water quenching leads to distortion in the profile and potential cracking in crush zones during crash tests.
  
  
  
• 6005A (Al-Si-Mg): Optimized for automotive engineering. It has low copper content, but "Dispersoid" hardening is achieved via Manganese (Mn) and Chromium (Cr) additions. Its greatest advantage is low quench sensitivity. Thin-walled profiles can achieve T6 properties with just air cooling. This maintains dimensional stability and, crucially, allows for perfect folding without cracking in axial crush tests. Its fatigue resistance is also superior to 6061.
  
  
  
• 6082 (Al-Si-Mg-Mn): The highest strength alloy of the 6000 series. Used in suspension arms and subframe parts. However, it is difficult to extrude (slow speeds) and has lower surface quality. Preferred only for non-visible parts requiring very high load-bearing capacity.
  
  
  

1.2 Electric Vehicle (EV) Battery Trays

The enclosure protecting the battery pack is an engineering marvel. These structures are typically massive trays (2m length x 1.5m width) produced entirely from aluminum extrusion profiles.

 

Design Requirements:

• Sealing: Batteries must be protected against water and moisture at IP67/IP68 levels.
  
  
  
• Fire Protection: Must isolate fire in case of thermal runaway.
  
  
  
• EMI Shielding: Aluminum's natural conductivity protects the battery from electromagnetic interference.
  
  
  

 

Manufacturing Method: The battery frame is usually constructed by joining multi-hollow profiles made of 6005A or 6063 alloys. These profiles are joined using corner blocks and Friction Stir Welding (FSW) or MIG welding. 6005A yields excellent results in FSW, with minimal strength loss in the weld zone.

 

1.3 Thermal Management: Cooling Plates

Maintaining battery cells at optimum operating temperatures (20-40°C) is vital. "Cooling Plates" are placed beneath battery modules. These are micro-port extrusion profiles through which a water-glycol mixture flows.

• Thermal Conductivity is the key parameter here.
  
  
  
• 6063 Alloy: Offers high thermal conductivity (~200-210 W/mK). It provides both structural strength and rapid heat transfer, making it the most common choice.
  
  
  
• 6061 Alloy: Due to higher alloying elements, its thermal conductivity is lower (~160-170 W/mK), potentially reducing cooling efficiency by 15-20%.
  
  
  

 

Future Trend: Integrated cooling floors, where the battery tray floor and cooling plate are combined, are on the rise. This requires pressing massive single-piece profiles (CCD > 300mm) with very thin channels, increasing the need for 4000+ ton press forces and advanced die technologies like Dievar.