7021 (7021-T6, AlZn5.5Mg1.5) Aluminum
7021 aluminum is a 7000-series aluminum alloy: the main alloying addition is zinc and it is formulated for primary forming into wrought products. Cited properties are appropriate for the T6 temper. To achieve this temper, the metal is solution heat-treated and artificially aged until it meets standard mechanical property requirements. 7021 is the Aluminum Association (AA) designation for this material. In European standards, it will be given as EN AW-7021. Additionally, the EN chemical designation is AlZn5,5Mg1,5. And the UNS number is A97021.
It originally received its standard designation in 1976.
The graph bars on the material properties cards below compare 7021 aluminum to: 7000-series alloys (top), all aluminum alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Elastic (Young's, Tensile) Modulus
69 GPa 10 x 106 psi
Elongation at Break
9.4 %
Fatigue Strength
150 MPa 22 x 103 psi
Poisson's Ratio
0.32
Shear Modulus
26 GPa 3.8 x 106 psi
Shear Strength
270 MPa 40 x 103 psi
Tensile Strength: Ultimate (UTS)
460 MPa 67 x 103 psi
Tensile Strength: Yield (Proof)
390 MPa 57 x 103 psi
Thermal Properties
Latent Heat of Fusion
380 J/g
Maximum Temperature: Mechanical
200 °C 380 °F
Melting Completion (Liquidus)
630 °C 1170 °F
Melting Onset (Solidus)
510 °C 940 °F
Specific Heat Capacity
870 J/kg-K 0.21 BTU/lb-°F
Thermal Conductivity
150 W/m-K 87 BTU/h-ft-°F
Thermal Expansion
24 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
38 % IACS
Electrical Conductivity: Equal Weight (Specific)
120 % IACS
Otherwise Unclassified Properties
Base Metal Price
9.5 % relative
Density
2.9 g/cm3 180 lb/ft3
Embodied Carbon
8.3 kg CO2/kg material
Embodied Energy
150 MJ/kg 65 x 103 BTU/lb
Embodied Water
1140 L/kg 140 gal/lb
Common Calculations
Resilience: Ultimate (Unit Rupture Work)
41 MJ/m3
Resilience: Unit (Modulus of Resilience)
1110 kJ/m3
Stiffness to Weight: Axial
13 points
Stiffness to Weight: Bending
47 points
Strength to Weight: Axial
44 points
Strength to Weight: Bending
45 points
Thermal Diffusivity
59 mm2/s
Thermal Shock Resistance
20 points
Alloy Composition
Among wrought aluminum alloys, the composition of 7021 aluminum is notable for containing a comparatively high amount of zinc (Zn) and including zirconium (Zr). Zinc is used to achieve significant increases in strength, at the cost of increased susceptibility to stress corrosion cracking. Among other things, this limits weldability. Zirconium is used to increase an alloy's recrystallization temperature, which increases the temperature at which the alloy can be used without permanent loss of mechanical properties.
| Al | 90.7 to 93.7 | |
| Zn | 5.0 to 6.0 | |
| Mg | 1.2 to 1.8 | |
| Fe | 0 to 0.4 | |
| Zr | 0.080 to 0.18 | |
| Si | 0 to 0.25 | |
| Cu | 0 to 0.25 | |
| Mn | 0 to 0.1 | |
| Ti | 0 to 0.1 | |
| Cr | 0 to 0.050 | |
| res. | 0 to 0.15 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
Handbook of Aluminum vol. 2: Alloy Production and Materials Manufacturing, George Totten and D. Scott MacKenzie (editors), 2003
Aluminum: Properties and Physical Metallurgy, John E. Hatch (editor), 1984
EN 755-2: Aluminium and aluminium alloys. Extruded rod/bar, tube and profiles. Mechanical properties
EN 485-2: Aluminium and aluminium alloys. Sheet, strip and plate. Mechanical properties
ASM Specialty Handbook: Aluminum and Aluminum Alloys, J. R. Davis (editor), 1993
ISO 6361-2: Wrought aluminium and aluminium alloys - Sheets, strips and plates - Part 2: Mechanical properties
EN 573-3: Aluminium and aluminium alloys. Chemical composition and form of wrought products. Chemical composition and form of products