Aluminium Grades

I always find machining aluminium to be mostly ok, but now and again milling can just go badly wrong if the chips stick to the tool. The following list of alloys will give you an idea as to how the different alloys can be used.


  • 99% or higher purity
  • excellent corrosion resistance
  • high thermal conductivity
  • high electrical conductivity
  • excellent workability


  • low mechanical properties


  • principal alloying element is copper
  • heat treated mechanical properties can exceed mild steel


  • solution heat treatment required to get optimum properties
  • corrosion resistance not as good as other aluminium alloys
  • tend to be brittle
  • exhibit poorer corrosion resistance than other alloy series.


  • free machining


  • principal alloying element is manganese – up to 1.5%
  • moderate strength
  • higher manganese alloys have good machinability
  • particularly resistant to pitting corrosion.


  • principal alloying element is silicon, in significant amounts it lowers the melting point
  • used in welding and brazing
  • most alloys non-heat treatable
  • good casting qualities


  • principal alloying element is magnesium
  • alloys with high magnesium and manganese result in high strength but non-heat treatable
  • good welding characteristics
  • anodize well
  • good resistance to corrosion even in marine environments


  • limited cold working
  • lower safe operating temperatures due to magnesium content


  • principal alloys silicon and magnesium
  • heat treatable
  • good formability
  • good corrosion resistance
  • medium strength
  • relatively easy to roll extrude and forge.


  • easy to machine
  • medium strength alloy
  • excellent corrosion resistance
  • common model engineering alloy, my 5 Cylinder Rotary engine uses this grade of aluminium extensively


  • free machining


  • principal alloy is Zinc
  • addition of magnesium results in heat-treatable and very high strength
  • sometimes other elements added such as copper and chromium


  • good resistance to aggressive atmospheres


  • may contain tin, iron or silicon
  • can be rolled to thin sheets
About Nigel 336 Articles
I've been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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