Aluminium Alloys

Aluminium Alloys

1. Heat treatable Wrought Aluminium Alloys

   • 2xxx series
     • Aging
       • Decomposition
       • +T = +mechanical prop.
       • Tmax = Tsolid
       • Overheating = - UTS, ductility
     • Solid solution hardening
       • High % Mg - CuMg4Al6 & CuMgAl2
       • Low % Mg - CuAl2
       • Low % Cu - Al3Mg2
     • 2024 alloy (Al-Cu)
       • Heat treatments: T3, T4, T6 & T8
     • Properties
       • High tensile strength Low corrosion Limited weldability
   • 8xxx series
     • Al + NI,Fe
     • Al + Si,,Ni,Cu
   • 6xxx series
     • Al + Mg,Si
     • strength: 6xxx<2xxx<7xxx
     • corrosion resistant
     • good formability, weldability and thermal conductivity
     • 6013 (Al-Mg-Si)
       • Aged at 170 ºC
       • Reduced corrosion resistance
       • Improved mechanical properties
   • 7xxx series
     • Al + Zn,Mg,Cu
     • Highest strength
     • Poor stress corrosion and weldability
     • Heat treatments: T6 and T7
   • Al-Li alloys
     • Lightness - Aerospace industry €€

2. Non Heat treatable Wrought Aluminium Alloys

   • Alloying elements
     • Improve mechanical properties
     • Decrease ductility, corrosion resistance and electric conductivity
   • 1xxx series Al 99%
     • Properties
       • High corrosion resistance, high thermal and electrical conductivity. low strength, easy plastic deformation ...
     • Electrical and chemical apps.
   • 3xxx series (Mn)
     • Properties
       • High ductility, good fomability. medium strength, weldability...
     • Apps. where good formability is required
   • 5xxx series (Mg)
     • Properties
       • Medium strength, good formability, good corrosion performance...
     • General apps.
       • Sheet fabrication
       • Marine
       • Automotive

3. Aluminium processing

   • Casting
     • Primary and secondary Al
     • Versatile techniques
   • Forging
     • Closed dies
     • 2xxx and 7xxx - heat treated after forging
   • Extrusion
     • 6xxx - good extrudability
     • 2xxx and 7xxx - more difficult to extrude
   • Rolling
     • after continuous casting
     • 2xxx (400 - 450 ºC)
     • 7xxx (400-440 ºC)
   • Forming
     • Highly formable at room T
     • Inmediately after quenching
     • forming tools made of hardened steels
   • Super Plastic Forming
     • allows sheet to elongate to large strains
     • make part shapes

4. Aluminium Joining

   • Joining techniques
     • Mechanical fastening
       • Bolts
       • Rivets
     • Adhesive bonding
     • Hybrid connections
     • Welding
       • Difficult to weld
       • Factor affecting welding
         • oxide layer
         • high thermal cond.
         • high coeff. of thermal expansion
         • high solidificartion shrinkage
         • high hydrogen solubility
       • Aerospace alloys
         • 6xxx - readily weldable 2xxx - fusion welded 7xxx - excessive strength loss 4xxx - filler metals used
       • Methods
         • GTAW
         • GMAW
         • Resistance welding
         • Laser welding
         • Friction welding
         • Friction stir welding

5. Cast Aliuminium alloys

   • A201.0
     • Highest strength casting alloy
     • Elevated temperature properties
     • Can be heat treated
     • UTS= 550 MPa and El= 10%
   • A357.0
     • Hypoeutectic Aluminium-Silicon alloys (4-%Si) + Cu, Mg and/or Mn
     • UTS= 320 Mpa and El= 1-6%
     • Effect of alloying elements
       • Mg (0.3-1%) : higher strength
       • Cu (1-4%) : higher strength at higher T

Images and files in the map