Considerations for Automotive Components

The performance of your extruded parts is driven by:

  • Geometry – or the profile design (e.g. internal webs, etc.)
  • Alloy chemistry – particularly the Mg and Si composition.
  • Microstructure – i.e.: grain size, structure, and geometry, thickness of the outer layer, etc.

Geometry 

The illustrations of successful extrusion designs for the various applications portrayed in the interactive applications guide show how profile design can help meet the most demanding requirements.

Alloy Chemistry

Cost Performance & Drivers 

Alloy performance – and cost - can be tailored by Mg and Si composition.  There are currently over 110 6xxx series alloys – the series most often used for extrusion – registered with the Aluminum Association.  Here is how a few of the alloys most frequently specified for auto applications compare:

Mg-Si Concentration and Strength chart

Note: While 6005A and 6008 have similar composition, 6008 has the addition of Vanadium which can lead to improved grain refinement and bend strength.

Common Aluminum Extrusion Alloys for Automotive Components

Alloy, Temper Yield Strength (Mpa) Ultimate Tensile (Mpa) % Elongation Surface Quality Bending Extrudability, Processing & Cost
6063, T6 170 205 8 (<3.2mm), 10 (>3.2mm) Excellent finish & corrosion resistance  Good Superior extrudability, Easy quench
6005A, T61 225 260 8 Superior corrosion resistance Good Superior extrudability & quench
6008, T6 215  270 8 Superior corrosion resistance Good Superior extrudability & quench
6061, T6 240 260 8 Good corrosion resistance  Manageable Good extrudability, quench demanding
6082, T6 260 310 6 Good corrosion resistance  Manageable  Good extrudability, very quench demanding 

Source: Rio Tinto Aluminum, Magnode, A Shape Corp. Company 
 

Extrudability & Conversion Cost of Extrusion Alloys

Aluminum Alloys 6005A, 6063 and 6082 are commonly used for automotive structures because their strength is close to mild steel, yet at one-third the density.  Note that as strength increases, “extrudability” – or the difficulty of producing the extrusion decreases, resulting in a higher conversion cost.

* T6, except 6005A at T61
** Given the range of compositions and processing paths for a given alloy, these characteristics should be considered typical; significant variations are possible. 
Source: Base data from Rio Tinto
 

Microstructure

Microstructure – i.e.:  grain size, structure, geometry and the thickness of the outer layer – is the third key variable in determining part performance.  Note that microstructure is determined by both chemistry and extrusion process parameters – especially extrusion temperature and quench speed.  It is particularly critical in managing extrusion straightness, twist, and bowing.

Recrystallized Grain

recrystallized grain structure
  • Most frequent type
  • Grain size ranges between 25 and 400 microns
  • Max grain size should be controlled for formability
     

Fibrous Grain

fibrous grain structure
  • Typically higher strength alloys with specific alloy elements Mn, Cr, Zr
  • Increased mechanical properties, increased fracture resistance
  • Reduced ductility
     

Mixed Grain Structure (Fibrous / Recrystallized) 

mixed grain structure
  • Fully fibrous grain may not be achievable, surface recrystallizes first
  • Recrystallized layer thickness needs to be specified; ductility, other mechanical properties may be impacted if recrystallized layer is too thick or grain size too large.
     

Partner with an Extruder 

As noted, microstructure is determined by both chemistry and extrusion process parameters, especially extrusion temperature and quench. Hence it is equipment and process specific.

Work closely with your extrusion partner to assure optimal extrusion performance and cost.

Ready to get started? Find an extruder