Chapter Two Aluminum Extrusion Alloys
Advantages of Aluminum Extrusions Aluminum s Material Advantages: Recyclable and Nontoxic Lightweight Strong High Strength to Weight Ratio Resilient Corrosion-Resistant Thermally Conductive Reflective Electrically Conductive Nonmagnetic Noncombustible and Non-sparking Cryogenically Strong Aluminum Extrusion s Process Advantages: Attractive Wide Range of Finishes Virtually Seamless Complex Integral Shapes Fastening and Assembly Joinable Fabrication Tolerancing Cost-Effective Short Lead Times
Temperature Classification of Extruded Metals
Aluminum Alloys Heat treatable and non heat treatable 2xxx, 6xxx, 7xxx (HT) 1xxx, 3xxx, 5xxx (NHT) Mechanical performance Product properties (Strength, ductility) Workability (during forming) Corrosion characteristics - composition Processing aspects Cost Applications
6xxx Alloys Profiles
Aluminum Alloys Designation Principal Alloying Element Typical Alloy Characteristics 1xxx Minimum 99% aluminum High corrosion resistance Excellent finishability Easily joined by all methods Low strength Poor machinability Excellent workability High electrical and thermal conductivity 2xxx Copper High strength Relatively low corrosion resistance Excellent machinability Heat treatable 3xxx Manganese Low to medium strength Good corrosion resistance Poor machinability Good workability 4xxx Silicon Not available as extruded products 5xxx Magnesium Low to moderate strength Excellent marine corrosion resistance Very good weldablity 6xxx Magnesium & Silicon Most popular extrusion alloy class Good extrudabilty Good strength Good corrosion resistance Good machinability Good weldability Good formability Heath treatable 7xxx Zinc Ver high strength Good machinability Heat treatable 8xxx Other ----------------------
Common Tempers O Fully annealed H112 Strain-hardened; used for non-heat-treatable alloys T1 Cooled from elevated temperature and naturally aged T4 Solution heat-treated and naturally aged T5 Cooled from elevated temperature and artificially aged T6 Solution heat-treated and artificially aged
Aluminum Extrusion Process Billet casting Homogenization Extrusion process Cooling/quenching Straightening ~1/2 % (plastic permanent deformation) 1-3% ( elimination of residual stresses) Precipitation treatment (age hardening) Finishing operations: Machining, Anodizing, Painting, Joining
Temperatures
Aluminum Extrusion Parameters Press Force 10-100 MN.ton Container Diameter 100-650 mm inches Flow Stress 300-1500 N/mm 2 ksi Billet Length 300-1500 mm inches Billet Temp. 450-550 o C F Exit Speed - High Extrudability 25-100 m/min.ft./min - Low Extrudability 0.5-10 m/min.ft./min Extrusion Ratio, R 20:1 to 100:1
Chemical Composition vs. Performance T6 Conditions
Phase Diagram
Al -Mg 2 Si
Extrusion Sequence
Press Quenching
Physical Simulation of Extrusion of 6xxx AA OBJECTIVES To predict the physical response of an aluminum alloy to specific processing conditions (temperature, strain, strain rate). Thermal cycle simulation homogenization through ageing Compression testing deformation modeling
Extrusion Thermal Cycle O. Reiso, Dr. Tech. Thesis, Trondheim, Norway, 1992.
Procedure Thermal Simulation High High Preheat Low Extrusion High Preheat High Extrusion Preheat (Gas or Induction) Low Low Preheat Low Extrusion Low Low Preheat High Extrusion High Extrusion (Exit Temperature)
Gleeble Setup Sample Jaws Quench Spray Head
Homogenized Microstructure 6063 AA SEM Image AlFeSi
Low Preheat (790 0 F) - Low Extrusion (925 0 F) Mg 2 Si 6063 AA Keller s etch 60 m AlFeSi
High Preheat (860 0 F) - High Extrusion (1040 0 F) 6063 AA Keller s etch 26 m AlFeSi
Low Preheat (790 0 F) - Low Extrusion (925 0 F) + T6 aged 6063 AA SEM Image Mg 2 Si 3 m
High Preheat (860 0 F) - High Extrusion (1040 0 F) + T6 age 6063 AA Keller s etch 26 m
1xxx Series (NHT) Super purity (SP) aluminum (99.99%) Commercial purity (CP) aluminum (99%) Low mechanical properties Annealed SP - YS: 7-11 MPa Decorative finish (architecture) Chemical process equipment Electrical conductors
3xxx Series (NHT) Al-Mn Mn up to 1.25% (solubility @ 1.82%) To avoid formation of Al 6 Mn - low ductility Al-Mn-Mg (3105; Al-0.55Mn-0.5Mg) Combination of properties Moderate strength High ductility Very good corrosion resistance
5xxx Series (NHT) Al-Mg alloys Medium strength alloys Good corrosion resistance Excellent resistance to marine environment Good extrudability UTS from 125 MPa (5005; Al-0.8Mg) to 310 MPa for 5456 in annealed conditions
2xxx Series (Al-Cu) (HT) High mechanical properties Enhanced age hardening by strain hardening T8 temper can be up to 35% stronger than T6 Good welding performance Complex physical metallurgy
2xxx Series (Al-Cu-Mg) (HT) Duraluminum discovered in Berlin in 1906 by Alfred Wilm (Al-3.5Cu-0.5-0.5Mg- 0.5Mg) Used for Zeppelin airships Alloy 2017 is a modified version of duraluminum Lower fracture toughness than 7xxx alloys
7xxx Series (HT) (Al-Zn-Mg-Cu) The strongest alloys in the Al family Cu added to improve resistance to stress corrosion cracking Significantly lower extrudability Aerospace application
8xxx Series Other alloys 8001 (Al-1.1Ni-0.6Fe) with excellent corrosion resistance 8011 (Al-0.75Fe-0.7Si) bottle caps because of very good ductility Amorphous aluminum alloys belong to this group as well
Homogenization Uniform chemistry (no chemical segregation) Uniform microstructure dendrites grain size alloying elements Elimination of casting defects
-Al 9 Fe 2 Si 2 Form at the interdendritic regions upon casting Almost a continuous network
AlFeSi Intermetallics
-Al8Fe2Si Form from pre-existing - during homogenization necklace structure
6063 Homogenization 25 um
Morphological Evolution Examine 3D AlFeSi particle morphology as function of heat treatment time Size, Shape, Interconnectivity Unhomog. -AlFeSi Homog. -AlFeSi
Case Study - Homogenization 2D and 3D Microstructure Characterization Tools Light Optical Microscopy (2D) Scanning Electron Microscopy (2D) EBSD (2D) and FIB (3D) Transmission Electron Microscopy
FIB Milling
2D and 3D Projections
3 D Morphology Import each 2D section into Matlab Input distance between each slice Plot using MathCad