24 July 2021 7000 Series Aluminum Alloy
7475 Aluminum Alloy Plate
7475 aluminum alloy is a controlled toughness alloy developed by Alcoa for sheet and plate applications that require a combination of high strength, superior fracture toughness and resistance to fatigue crack propagation. Typical fracture toughness values for alloy 7475 plate are approximately 40 percent greater than alloy 7075 in the same tempers.
Corrosion resistance and fatigue behavior of alloy 7475 are equal to and, in some cases, better than many of the current high strength aerospace alloys such as 7075, 7050 and 2024. Alloy 7475 sheet is available as bare and alclad in the T61 and T761 tempers. Plate is available in T651, T7651 and T7351 tempers. Alcoa guarantees a minimum fracture toughness level along with standard minimum tensile properties for alloy 7475 plate and sheet products in all available temper conditions except “O”.
Chemical Composition:
| Chemical Elements | Metric | English |
|---|---|---|
| Aluminum, Al | 88.5 - 91.5 % | 88.5 - 91.5 % |
| Chromium, Cr | 0.18 - 0.25 % | 0.18 - 0.25 % |
| Copper, Cu | 1.2 - 1.9 % | 1.2 - 1.9 % |
| Iron, Fe | <= 0.12 % | <= 0.12 % |
| Magnesium, Mg | 1.9 - 2.6 % | 1.9 - 2.6 % |
| Manganese, Mn | <= 0.06 % | <= 0.06 % |
| Other, each | <= 0.05 % | <= 0.05 % |
| Other, total | <= 0.15 % | <= 0.15 % |
| Silicon, Si | <= 0.10 % | <= 0.10 % |
| Titanium, Ti | <= 0.06 % | <= 0.06 % |
| Zinc, Zn | 5.2 - 6.2 % | 5.2 - 6.2 % |
Mechanical Properties:
| Mechanical Properties | Metric | English | Comments |
|---|---|---|---|
| Hardness, Brinell | 135 | 135 | 500 kg load with 10 mm ball. Calculated value. |
| Hardness, Knoop | 170 | 170 | Converted from Brinell Hardness Value |
| Hardness, Rockwell A | 50.5 | 50.5 | Converted from Brinell Hardness Value |
| Hardness, Rockwell B | 82 | 82 | Converted from Brinell Hardness Value |
| Hardness, Vickers | 155 | 155 | Converted from Brinell Hardness Value |
| Tensile Strength, Ultimate | 496 MPa | 72000 psi | AA; Typical |
| Tensile Strength, Yield | 421 MPa | 61000 psi | AA; Typical |
| Elongation at Break | 13 % @Diameter 12.7 mm | 13 % @Diameter 0.500 in | AA; Typical |
| Modulus of Elasticity | 71.7 GPa | 10400 ksi | AA; Typical; Average of tension and compression. Compression modulus is about 2% greater than tensile modulus. |
| Compressive Yield Strength | 380 MPa | 55100 psi | 0.1% Permanent Set |
| Poissons Ratio | 0.33 | 0.33 | |
| Fatigue Strength | 220 MPa @# of Cycles 1.00e+7 | 31900 psi @# of Cycles 1.00e+7 | |
| Fracture Toughness | 35.2 MPa-m½ | 32.0 ksi-in½ | plate; S-L |
| 36.0 MPa-m½ | 32.8 ksi-in½ | K(IC) in S-L Direction | |
| 41.8 MPa-m½ | 38.0 ksi-in½ | plate; T-L | |
| 45.0 MPa-m½ | 41.0 ksi-in½ | K(IC) in T-L Direction | |
| 52.7 MPa-m½ | 48.0 ksi-in½ | plate; L-T | |
| 55.0 MPa-m½ | 50.1 ksi-in½ | K(IC) in L-T Direction | |
| Machinability | 70 % | 70 % | 0-100 Scale of Aluminum Alloys |
| Shear Modulus | 27.0 GPa | 3920 ksi | |
| Shear Strength | 300 MPa | 43500 psi | Calculated value. |
Thermal Properties:
| Thermal Properties | Metric | English | Comments |
|---|---|---|---|
| CTE, linear | 21.6 µm/m-°C @Temperature -50.0 - 20.0 °C | 12.0 µin/in-°F @Temperature -58.0 - 68.0 °F | |
| 23.2 µm/m-°C @Temperature 20.0 - 100 °C | 12.9 µin/in-°F @Temperature 68.0 - 212 °F | AA; Typical; average over range | |
| 23.4 µm/m-°C @Temperature 20.0 - 100 °C | 13.0 µin/in-°F @Temperature 68.0 - 212 °F | ||
| 24.3 µm/m-°C @Temperature 20.0 - 200 °C | 13.5 µin/in-°F @Temperature 68.0 - 392 °F | ||
| 25.2 µm/m-°C @Temperature 20.0 - 300 °C | 14.0 µin/in-°F @Temperature 68.0 - 572 °F | ||
| Specific Heat Capacity | 0.880 J/g-°C | 0.210 BTU/lb-°F | Estimated from trends in similar Al alloys. |
| Thermal Conductivity | 163 W/m-K | 1130 BTU-in/hr-ft²-°F | AA; Typical at 77°F |
| Melting Point | 477 - 635.0 °C | 890 - 1175 °F | AA; Typical range based on typical composition for wrought products >= 1/4 in. thickness |
| Solidus | 477 °C | 890 °F | AA; Typical |
| Liquidus | 635.0 °C | 1175 °F | AA; Typical |
Process Properties:
| Processing Properties | Metric | English | Comments |
|---|---|---|---|
| Annealing Temperature | 413 °C | 775 °F | |
| Solution Temperature | 516 °C | 960 °F | must be preceded by soak at 870 to 890°F |
| Aging Temperature | 121 - 177 °C | 250 - 350 °F |
Fracture Toughness:
Alloy 7475 sheet is available bare or alclad in the T61 and T761 tempers. Bare and alclad 7475-T761 sheet has been the preferred sheet product for aerospace applications because of its resistance to general and exfoliation corrosion combined with higher toughness in comparison with bare and alclad 7475-T61 sheet. On the basis of tensile yield strength, 7475 sheet offers a significantly better combination of strength and toughness than either 2024-T3 or 7075-T6.